2  combustion code for Otto 2-Stroke-Cycle Piston engines. British to American
"A" Body The letter Chevrolet used for the Chevelle/El Camino line Around the world there are some differences in the words used to describe things in the automotive field.
"B" Body The letter Chevrolet used for the full size cars including, Impala, Impala SS, Caprice, Belair, Biscayne, etc. Accumulator = battery, car battery
"C" Body The letter Chevrolet used for the 2 wheel drive truck line Bonnet = hood
"F" Body The letter Chevrolet used for the Camaro line Boot = trunk
"G" Body The letter Chevrolet used for the Monte Carlo line Dynamo = generator
"H" Body The letter Chevrolet used for the Vega/Monza line Earth wire = ground wire
"K" Body The letter Chevrolet used for the 4 wheel drive truck line Follower or tappet = lifter (tappet also used in the US, mostly in reference to the type of cam, i.e. "flat tappet").
"X" Body The letter Chevrolet used for the Chevy II/Nova line Harmonic balancer/damper = crankshaft pulley
"Y" Body The letter Chevrolet used for the Corvette Inlet manifold = intake manifold
#1 condition A car in show condition or perfect Lorry = truck
#2 condition A car in excellent original condition showing minor wear/use or one with a quality restoration Number plate = license plate
#3 condition A car that is a typical driver in good condition Petrol = gasoline
#4 condition A car that runs well and is all there but considered a "beater" Saloon = "sedan" or 4-door car
#5 condition A basket case or a car that is good for parts "Semi" = duplex, duplex house; U.S. "semi" = tractor-trailer truck rig
.030 Over A term used when an engines cylinders have been enlarged or bored out .30 thousands of an inch over stock; can also be .010, .020, etc Windscreen (automotive) = windshield
1 bbl One barrel carburetor Wing (older vehicles) = fender, bumper
1. 1G  Ford 1st-Generation alternator, which uses an external fan, a V-belt pulley, & a remote 5-pin voltage regulator with grounded case to produce 35-90A, typically used on carburetor engines until the mid-80s. Reliable, but weak.
1st generation Camaro A term used to identify 1967-1969 Camaro's
2 bbl Two barrel carburetor
2 SPD 2 speed transmission
2-cycle  (slang) See Two-Stroke Cycle.
2G  Ford 2nd-Generation alternator, which uses an external fan & external 3-pin voltage regulator to produce 60-100A, typically used on early fuel-injected engines from the mid-80s to the early 90s. Famous for catching fire, usually due to a poor connection at the rectifier.
2nd generation Camaro A term used to identify 1970-1981 Camaro's
2-stroke  (slang) See Two-Stroke Cycle.
2-stroke cycle  See Two-Stroke Cycle.
2V  1) 2 Valves per cylinder; 2) 2 Venturi (barrel) (carburetor/vacuum).
2WD 2 Wheel drive
2WD  Two Wheel Drive. A powertrain system which delivers engine power to only one axle (either front or rear). AKA 4X2. Contrast RWD, AWD, FWD, 4WD.
2X4 Two-four barrel carburetors or 2 wheel drive
3 duece's Three two barrel carburetors
3 SPD 3 speed transmission
3-2 Timing Solenoid (3-2TS)  A device that controls the timing valve.
3G  Ford 3rd-Generation alternator, which uses an internal fan, multi-rib pulley, & external 3-pin voltage regulator (later versions only utilizing 2 of the pins) to produce 90-130A, used from the early 90s to the early 00s with much success. Noted for reliability & high output at all RPMs, and for being easy to retrofit into older vehicles.
3rd generation Camaro A term used to identify 1982-1992 Camaro's
3X2 Three two barrel carburetors
4 bbl Four barrel carburetor
4 SPD 4 speed transmission
4-cycle  (slang) See Four-Stroke Cycle.
4G  Ford 4th-Generation alternator, which uses an internal fan & 3-pin voltage regulator (only utilizing 2 of the pins), and a multi-rib pulley to produce 90-130A, used from the early 00s to the late 00s.
4R100  4 speed, Rear wheel drive, 1000 lb-ft, electronic transmission, formerly known as E4OD.
4R44E  4 speed, Rear wheel drive, 440 lb-ft, Electronic transmission, derived from the C3/A4LD.
4R55E  4 speed, Rear wheel drive, 550 lb-ft, Electronic transmission, derived from the C3/A4LD.
4R70W  4 speed, Rear wheel drive, 700 lb-ft, Wide ratio electronic transmission, formerly known as AODE and AODE-W.
4-stroke  (slang) See Four-Stroke Cycle.
4-stroke cycle  See Four-Stroke Cycle.
4th generation Camaro A term used to identify 1993-present Camaro's
4V  1) 4 Valves per cylinder; 2) 4 Venturi (barrel) (carburetor/vacuum).
4WD 4 Wheel drive
4WD  Four Wheel Drive. A powertrain system which delivers engine power to differentials in both (front & rear) axles. AKA 4X4. Contrast RWD, AWD, FWD, 2WD.
4X2  See 2WD.
4X4 Four wheel drive
4X4  See 4WD.
4x4 Low (4x4L)  Indicates the 4x4 Low range of the transfer case has been selected.
4x4L  4x4 Low.
4x4x2  A power steering gear box for early Broncos made from a '75-79 4WD case and early '80s 2WD internals to get the proper direction.
5G  Ford 5th-Generation alternator, which uses an internal fan & 3-pin voltage regulator under PCM control, and a multi-rib 1-way clutched pulley to produce 100-150A, used from the late 00s onward.
5R110  5 speed, Rear wheel drive, 1100 lb-ft electronic truck transmission, derived from the C6/E4OD.
5R55W  5 speed, Rear wheel drive, 550 lb-ft, Wide-ratio electronic truck transmission, derived from the C3/A4LD.
5th Wheel  see Fifth Wheel.
A  1) Ampere; 2) combustion code for Other
A    Amperes
A.P.I. Amercian Petroleum Institute
A/C  Air Conditioning.
A/C    Air Conditioning
A/CL  Air Cleaner (carburetor/vacuum)
A/CL BI MET  Air Cleaner BiMetallic valve (carburetor/vacuum)
A/CL DV  Air Cleaner Diverter Valve (carburetor/vacuum)
A/D  Analog-to-Digital signal conversion.
A/F    Air/Fuel Ratio
A/R As required
A/T  Automatic Transmission/Transaxle.
A/T    Automatic Transmission/Transaxle
A-Arm  A suspension strut shaped like a horizontal "A", with the legs attached to the vehicle frame & the top attached by a ball joint to the steering knuckle.
ABRS    Air Bag Restraint System
ABS Anti lock brake system
ABS  1. Anti-lock Brake System; 2. A sensor, signal or circuit which supplies rear axle speed data either to the RABS (or RABS-II) module, the 4WABS module, the PSOM, &/or the EEC (for electronic automatic transmission control & return-to-idle). After processing by the 4WABS module &/or the PSOM, the signal is also fed to the VSC & the Bronco overhead console (for temperature adjustment); 3. A type of plastic. Compare PVC. 
ABS    Anti Lock Brakes
Absolute Pressure  The pressure referenced to a perfect vacuum. Contrast gauge pressure, which references atmospheric pressure (~14.7psi above perfect vacuum).
AC    Alternating Current
AC, A.C. Air conditioning
ACC  Air Conditioning Clutch. 
Accordion  See Crumple Zone.
ACCS  Air Conditioning Cycling Switch.
ACCS    A/C Cycling Switch
ACCUM    Accumulator
ACCY    Accessory
ACD  Air Conditioning Demand.
ACET  Air Conditioning Evaporator Temperature. AKA Evaporator Air Discharge Temperature 
ACON  Air Conditioning On.
ACP  Air Conditioning Pressure.
ACPSW  Air Conditioning Pressure Switch.
ACT  Air Charge Temperature sensor. AKA IAT.
ACT    Air Charge Temperature Sensor
Actuator  A mechanism for moving or controlling something indirectly instead of by hand.
ACV  Air Control Valve (carburetor/vacuum)
Adaption  Adjustments to the operating strategy made by the PCM based on actual driving conditions & feedback. Adaptions are stored in KAM separate from DTCs & freeze frames. Clearing adaptions is a special function available only on certain scanners, but it also occurs if KAPWR or KAM fails. Without adaptions, the PCM operates on baseline PROM strategy until it relearns the adaptions, which typically requires varied driving over 10-20 miles.
ADV    Advance
Advance  1) the quality or quantity of ignition timing BTDC; 2) an auto parts store chain.
AFB, Carter AFB "Aluminum four barrel" A 4 barrel carburetor made by Carter
AFCM  Alternative Fuel Control Module. 
AFR    Air Fuel Ratio (also see below)
A-Frame  A supporting structure used for lifting overhead loads. It may consist of a single "A"-shaped boom which pivots (as on inexpensive wreckers or on light-duty cranes), or 2 with a single beam between them to span a working area below.
AFS    Airflow Sensor
Aftermarket  1. A general term for the industry that produces non-original parts for vehicles; see SEMA. 2. Non-original vehicle parts. Contrast Direct-Replacement.
Ah  Amp hours
AI    Air Injection
AIR  Secondary Air Injection.
AIR BPV  Air ByPass Valve. AKA TAB (carburetor/vacuum)
Air Conditioning (A/C)  A vehicular accessory refrigeration system that modifies the passenger compartment air by cooling and drying the air using a belt-driven compressor with magnetic clutch, a condenser with fan, an orifice or expansion valve, an evaporator within an air handler, an accumulator/drier with dessicant, and various sensors & switches. As the refrigerant gas is compressed, its temperature rises, and it flows as a hot high-pressure gas into the condenser. The external airflow created by the fan cools the refrigerant (carrying heat away) so that it condenses to a warm high-pressure liquid. This liquid flows through the orifice tube or expansion valve, which creates a sudden pressure drop. The low-pressure liquid boils & becomes cold, collecting heat from the evaporator core, which in turn gets heat from the air within the passenger cabin. The cool low-pressure gas & liquid mix flows into the accumulator where any water is absorbed by the dessicant. The accumulator is designed to allow only gas to flow out & return to the compressor to repeat the cycle. If the cabin temperature is too low to boil the refrigerant, the low-side pressure falls below ~20psi, breaking the circuit to the compressor clutch. This prevents ice from forming on the evaporator AND prevents the system from ever dropping below atmospheric pressure, which could pull in contaminants. Early systems used R-12, but all systems now use R-134a.
Air Conditioning Clutch (ACC)  A sensor, signal, or circuit which indicates status of the A/C clutch.
Air Conditioning Cycling Switch (ACCS)  A sensor, signal, or circuit which indicates status of the A/C cycling switch.
Air Conditioning Demand (ACD)  A sensor, signal, or circuit which indicates status of the A/C demand switch.
Air Conditioning On (ACON)  A sensor, signal, or circuit which indicates status of the A/C system.
Air Conditioning Pressure (ACP)  A sensor, signal, or circuit which indicates pressure in the A/C system.
Air Conditioning Pressure Switch (ACPSW)  A switch used for additional A/C system pressure control. Also referred to as the refrigerant containment/fan function switch.
Air Injection One method of reducing harmful exhaust emissions by injecting air into each of the exhaust ports of an engine. The fresh air entering the hot exhaust manifold causes any remaining fuel to be burned before it can exit the tailpipe.
AIR or A.I.R.    Air Injection Reactor
AIR, A.I.R. Air injection reactor
Air/fuel ratio The ratio of air to gasoline by weight in the fuel mixture drawn into the engine.
Air/Fuel Ratio  Air to fuel mixture ratio; 14.7 1 is also called stoichiometry. This value is monitored & stored by the PCM as the LAMBSE PID.
AIRB  Secondary Air Injection Bypass. AKA TAB
AIRD  Secondary Air Injection Diverter. AKA TAD
Air-to-Air (A2A)  a heat exchanger such as an intercooler for a forced-induction system.
AIS    Air Injection System
AKA  also known as.
Al  Aluminum.
ALDL    Assembly Line Data Link
Allen Key or Allen Wrench  A hardened driver whose functional end (if not the entire tool) is a male hex. Contrast Torx.
alt, Alt, Alternator A device used for converting mechanical energy into electical energy.
Alt.    Alternator or Altitude
Alternator  A term trademarked by Chrysler Corporation. See Generator.
ALVW  Adjusted Loaded Vehicle Weight, defined by (Curb Weight + GVWR)/2, or Curb Weight + (Payload/2).
Ambient Temperature  Temperature of the air surrounding an object.
AMG  1) mega fuse; 2) a German customizing company for BMW & Mercedes; 3) American Motors General, the manufacturing consortium for many US military vehicles
Ammeter An instrument calibrated in amperes. It is used to measure the flow of an electrical current in a circuit.
Amp  1) Amplifier; 2) (slang) Ampere
Amp    /amp/amps: Ampere
Ampere The rate of flow of electrical current present when one volt of electrical pressure is applied against one ohm of electrical resistance.
Ampere (A or i)  the standard unit of measure for electrical current. It represents a specific number of electrons flowing past a given point per second, analogous to the flow rate of water.
AN Fittings  Army/Navy fittings; a shape & sizing convention used on many military vehicles, and popular on modified civilian vehicles for its reliability & interchangeability. Sizes are preceded by a minus sign and represent the inside diameter in INCHES times 16 (-AN = inch x 16), so a -6AN fitting is 6/16" or 3/8" ID.
Anaerobic  a chemical (usually an adhesive or sealant) that cures without being exposed to air, such as epoxy.
Analog  1. An electrical signal that can attain any value within the voltage limits of the signal, OR a mechanical display capable of any intermediate value. Contrast Digital 2. A substitue or simulation that functions similarly to the actual item.
Analog Meter  A handheld tool with an analog (needle) display for measuring various characteristics of electrical/electronic circuits & components. Contrast DMM.
Anti-lock Brake System (ABS)  An electro-hydraulic system which prevents wheel lockup during an emergency stop by modulating brake pressure. Allows the driver to maintain steering control and stop the vehicle in the shortest possible distance under most conditions. Several versions exist including RABS, RABS-II, 3-channel 4WABS, 4-channel 4WABS, TA, & TC. 
AOD  Automatic Overdrive transmission, derived from the FMX. It evolved into the AODE, 4R70W, 4R44E, 4R55E, 5R55W.
AODE  Automatic Overdrive Electronic transmission, derived from the AOD (FMX). It evolved into the 4R70W, 4R44E, 4R55E, 5R55W. AKA AODE-W.
A-Pillar  The front-most body structure for supporting the roof of a vehicle. Subsequent pillars are designated "B", "C", etc.
APM  mini blade fuse. AKA ATM.
APPS    Accelerator Pedal Position Sensor
APR  standard or regular blade fuse. AKA ATC, ATO.
APS  micro or mini low-profile blade fuse. AKA ATM.
APS    Absolute Pressure Sensor
APX  maxi blade fuse.
ARB  An aftermarket manufacturer of bumpers & a pneumatic selectable-locking differential. Compare E-Locker.
ARC  Automatic Ride Control.
armature A laminated soft iron core wrapped by a wire that converts electrical energy to mechanical energy as in a motor or relay.
ARS Air restraint system. (air bags)
Articulation  Movement of the suspension, especially to its extremes (front & rear suspensions in opposite directions) when off-roading.
ASCII  American Standard Code for Information Interchange; a standardized digital binary code of letters, numbers, & symbols used in most computers. 
ASCS    Air Suction Control Solenoid
ASD    Auto Shutdown
ASDM    Air Bag System Diagnostic Module
ASE Automotive service excellence
ASE  Automotive Service Excellence; an organization that establishes & maintains standards in the auto service industry, most notably by adminstering tests for technicians & other auto service personnel. 
ASME American society of mechanical engineers
ASSY, assy Assembly
ASV    Air Suction Valve
AT, auto, Auto Automatic transmission
ATC  standard or regular blade fuse. AKA APR, ATO.
ATC    Automatic Temperature Control
ATDC  After Top Dead Center; a time or angle of a given crankshaft lobe (usually #1) just after it has aligned with its connecting rod, and the piston is moving toward the crankshaft.
ATDC    After Top Dead Center
ATF  Type A, Type F, Mercon (I-V), MerconSP, MerconLV, FNR5, CVT, Dexron (I-V), ATF+2, ATF+3, ATF+4. Automatic Transmission Fluid; any of several non-compatible types of hydraulic oil, used in automatic transmissions, power steering systems, hydraulic brake boosters, manual transmissions, & transfer cases. Examples include
ATF    Automatic Transmission Fluid
ATM  mini, micro, or mini low-profile blade fuse. AKA APM, APS.
ATO  standard or regular blade fuse. AKA ATC, APR.
atomization The breaking down of a liquid into a fine mist that can be suspended in air.
ATS    Air Temperature Sensor
Automatic Ride Control (ARC)  A system that automatically adjusts the suspension system to accommodate varying road and driving conditions.
Averaging Bank/Trade  Used for Nox Credits on Heavy Duty Trucks Only. 
AWD All Wheel drive
AWD  All Wheel Drive. A powertrain system which delivers engine power through a differential in the transfer case to differentials in each axle. Some newer cheap AWD systems use a viscous coupling between the front & rear axles instead of a differential. Contrast RWD, FWD, 4WD, 2WD.
AWD    All Wheel Drive
AWG  American Wire Gauge; a number representing the effective cross-sectional area of an electrical conductor. The standard scale ranges from 0000 (0.460", ~12 mm) to 36 (0.005", ~0.13 mm) in 39 steps, with each higher gauge having 0.890526 the area of the preceding gauge. Stranded wire has a larger actual cross-section than solid wire of the same gauge due to the air spaces between the strands.
AX4N  Automatic 4 speed Non-synchronous transaxle (front-wheel drive).
AX4S  Automatic 4-speed Synchronous transaxle (front-wheel drive).
axial play Movement parallel to a shaft of bearing bore.
Axle  A structure which bears the weight of a chassis onto wheels, through bearings & hubs. Driven axles also contain mechanisms to transmit torque to the hubs. Steering axles further contain mechanisms to allow the wheels to swivel. Axles may be solid (monobeam) or independent. Each hub may be attached to 1 or 2 wheels.
Axle Wrap  A condition that affects leaf spring solid axle suspensions in which the spring pack isn't strong enough to withstand the torque under hard acceleration, and it flexes into an "S", slightly wrapping around the axle tube. Eventually, the tire breaks free, the torque is released violently, and the driveline suffers (usually catastrophic) impacts as the tires bounce and catch. There are several ways to reduce or eliminate the condition, including stronger springs, traction bars, or a multi-link suspension.
B/P    Backpressure
B+  Battery Positive Voltage.
B+    Battery Positive Voltage
BA Belair
BAC     By Pass Air Control
back pressure Restrictions in the exhaust system that slow the exit of exhaust gases from the combustion chamber.
backfire The sudden combustion of gases in the intake or exhaust system that results in a loud explosion.
Backfire  Combustion that occurs in the intake, causing flame & noise to emanate from the throttle. It can be caused by incorrect valve or ignition timing, a lean mixture, or fuel leaks. It can damage the carburetor, the throttle plates, sensors, the intake ductwork, anything under the hood, the hood, or even start a fire.
backlash The clearance of play between two parts such as meshed gears.
Backout  a failure of a terminal to remain mechanically in-place within its connector shell. The terminal is pushed back within the shell, preventing it from making good contact with the mating terminal, resulting in an open circuit, or intermittent open circuit, or high resistance.
Backspace (wheel offset) This is the distance from the rear mounting surface of the wheel to the rear edge of the rim.  Example
Back-tap  A special tap used for chasing damaged threads. Its cutting edges compress so the tool can be inserted past the damage, and then expanded to engage the good threads before working backward out of the hole.
Balanced An engine that has had the weights of it's internal moving parts (such as pistons) matched.
Ball Joint (BJ)  A spherical joint used mainly to connect a steering knuckle to a suspension arm; it has largely replaced the kingpin since it eases design & manufacture, and it allows fine & coarse adjustments for wheel alignment.
BAP  Barometric Absolute Pressure Sensor
BARO  Barometric Pressure.
BARO    Barometric
Barometric Pressure (BARO)  A sensor, signal, or circuit which indicates the pressure of the surrounding air at any given temperature and altitude. See MAP.
Barrel Roll  A side roll all the way back onto the wheels at least once.
Base Idle  Idle rpm determined by the throttle lever hardset on the throttle body with the IAC solenoid disconnected. It is preset at the factory & should never be adjusted.
Base Timing  Spark advance in degrees before top dead center of the base engine without any control from the PCM or ICM (EFI), or any vacuum- or centrifugal advance (carb).
BAT, BATT Battery
Batt.    Battery
BATTEMP  Battery Temperature.
Battery  An electrical storage device designed to produce a DC voltage by means of an electrochemical reaction. Common automotive batteries develop ~13.2VDC using six 2.2V lead & sulfuric acid cells, with the negative (-) terminal grounded to the chassis, body, & engine.
Battery Positive Voltage (B+)  The voltage from the battery positive post or any circuit connected directly to the battery, relative to the battery negative post, or chassis ground. Compare VPWR, VREF.
Battery Saver  a circuit for key-off accessories controlled by a module to disable the circuit after a preset time (usually 15 minutes). Compare Retained Accessory Power.
BBC, bbc Big block Chevy engine
BBL  Barrel (carburetor/vacuum). Compare Venturi.
bbl, BBL barrel (carburetor)
Bbl.    Barrel (Example: 4 Bbl.)
BCCC, BC/CC, B.C.C.C. Base Coat, Clear Coat. A Urethane paint with a clear coat over it
BCI  Battery Council International, a non-profit trade organization that establishes standards for autmotive batteries; particularly, physical sizes.
BCM  Body Control Module - an electronic component that generally controls systems unrelated to the powertrain. AKA GEM, BSM, CSM...
BCM    Body Control Module
Bench-Testing  1) testing a part or system on a fixture that simulates normal use; 2) (slang) guessing about the way something will work.
Bendix  1) A manufacturer of OE & direct-replacement auto parts; 2) (slang) A one-way starter drive gear.
Bevel Gears  A common gear design resulting in an angled drive. The radial gear teeth are on an angled surface (like a truncated cone), and their axes intersect where the tips of the cones would be, typically in a right angle. Contrast Helical, Herringbone, Hypoid, Spur, Worm.
BFH  (slang) Big F*****g Hammer.
BHP    Brake Horsepower
BI  fuel code for Other Bi-Fuel 
Bigblock  An engine family of varying displacements that share some parts & characteristics, most of which have higher displacement than most of those in another family of engines from the same manufacturer within the same model year range. Contrast Smallblock, Short Block, Long Block.
Billet  A dense form of metal (usually Aluminum) made by mechanically compressing a cast ingot to eliminate any internal pores, and then re-heating (annealing) it to relieve internal stress & re-crystallize it.
Binary  a simple numbering system using only two possible characters (usually 0 & 1) in each digit. "Bi-" means two. The binary representation of one is "1" or "00000001" (any amount of preceding 0s); two is "10"; three is "11"; nine is "1001"; fourteen is "1110". 8-bit binary contains 8 digits per value (byte, word); 16-bit contains 16 characters per value, so two in 16-bit binary is "0000000000000010".
Bit  a digital position within a numeral, capable of containing any valid character used in that numbering system.
BJB  Battery Junction Box.
Bk  Black wire or vacuum line.
BL  Body Lift.
Blade Fuse  A plastic-encased flat fuse with parallel flat terminals that replaced the glass tube fuse in the early 80s. Sizes are APS/ATM Low Profile/Micro, APM/ATM Mini, APR/ATC/ATO Blade, and APX/Maxi, ranging from 0.5A to 150A.
Blinker Fluid  A joke among mechanics & gearheads to detect amateurs. See KaleCo Automotive.
Block Test  See Dissolved Gas Test.
Blower (BLR)  A device designed to supply a current of air at a moderate pressure, typically through a ventilation system. It usually consists of an impeller assembly, a motor and a suitable case. The blower case may also function as part of the ventilation system and contain diverter doors and other apparatus.
BLR  Blower.
Blue Wrench  (slang) a torch, because of its blue flame. AKA Red Wrench because it makes things red-hot.
BMAP    Barometric and Manifold Absolute Pressure Sensor
BMC * Brake master cylinder
Bn  Brown wire or vacuum line.
Body Lift (BL)  The modification of a vehicle's ride height by spacing the body up from the frame, usually to allow for larger tires. It does not increase ground clearance, suspension travel, or approach/breakover/departure angles. It increases body sway, and the danger of the body shifting on the frame during a collision. Steering & shifting linkages usually must be adjusted, and hoses lengthened. See Lift. Contrast Tire Lift, Suspension Lift.
Body Mount  a rubber isolator (sometimes with steel sleeves) between the frame & cab. AKA Cab Mount.
Bolt  A medium- or heavy-duty machine-threaded fastener, generally with a hex head to be driven by a wrench into either a threaded hole or a nut. See Grade. Contrast Screw.
BOO    Brake On Off Switch
Boom  A low resonant sound, like a drum roll or distant thunder.
Booster Cables  A pair of light or medium wires with a connector or clamps capable of supplying under 120A from one vehicle to another for the purpose of recharging a weak battery over several minutes before attempting to crank the engine. Contrast Jumper Cables.
Booster Pack  See Jumper Battery.
BOP, B.O.P. Buick, Oldsmobile, Pontiac.
Bored, Bored out An engines cylinders have been enlarged or bored out. Also see; .030 over, punched
Bowtie A Chevrolet car
Box Van  A modified vehicle body using the cab & hood of a van or light truck, with a simple enclosed cargo box conjoined, like most ambulances.
Boxed or Boxed Frame  A frame constructed of hollow tubular members, as opposed to open channel members. It may be designed that way, or the result of adding material to a channel frame to enclose the members. Early Broncos & most Land Rovers have fully-boxed frames from the factory. '80-96 F-series & Broncos are only factory-boxed between the front bumper and the back of the first crossmember.
BPA  Bypass Air; see IAC.
BPA-ISC  Bypass Air Idle Speed Control solenoid; see IAC.
BPH  Ball-Peen Hammer; a steel hammer with one flat face & one hemispherical face for peening rivets, and other metalwork.
BPP  Brake Pedal Position. 
BPS    Barometric Pressure Sensor
BPT    Backpressure Transducer
Br  Brown wire or vacuum line.
Brake On/Off (BOO)  A binary switch which indicates the position of the brake pedal &/or activates the brake lights. It may also perform other functions. Compare BPP, Stop Lamp Switch.
Brake or Brakes  1) a system for slowing a moving vehicle, or holding it stationary; 2) the pedal, lever, or other mechanical components to control such a system; 3) the friction components of such a system.
Brake Pedal Position (BPP)  A multi-contact or analog sensor, signal, or circuit which indicates the position of the brake pedal for use by the traction control &/or restraint systems. Compare BOO.
Break  1) to fail, fracture, or shatter; 2) to free, loosen, or unseize.
Breakout Box  A service tool that "tees" between the PCM and the matching harness connector. The breakout box contains test pins that can be probed for EEC system testing without the risk of damage to the EEC, its wiring, or its connector by direct probing.
BRG * Bearing
Brinelling  the process by which bearings damage their own races due to LACK of movement under high loading. The race develops an imprint of the loaded bearing, resulting in looseness, noise, and accelerated wear.
BRKT, brkt * Bracket
BSM  Body Security Module, AKA BCM, CSM, GEM...
BTDC  Before Top Dead Center; a time or angle of a given crankshaft lobe (usually #1) just before it has aligned with its connecting rod, and the piston is approaching its maximum distance from the crankshaft. Ignition spark usually occurs during this phase.
BTDC    Before Top Dead Center
BTM Bottom
BTU    British Thermal Unit
Bu  Blue wire or vacuum line.
Build Sheet A sheet that was used by assembly line workers to build the car. This sheet listed options and also the original dealer that sold the car. 
Bumpstick Camshaft
Bus positive or negative (Bus+ or -)  Circuits that carry data to & from the various modules on a network, & the DLC.
Bus+ or -  Bus positive or negative. 
Buzz  A steady low-pitched noise, typically accompanied by a vibration.
BV  Bowl Vent (carburetor/vacuum)
BW 1345  A rare chain-driven 4WD (no internal differential) part-time 2-speed transfer case built by Borg-Warner with a fixed front yoke output on the L side. It replaced the NP 208F for a few years in heavy-duty light trucks until it was replaced by the 1356, and was always built with a fixed rear output yoke.
BW 1356  A common chain-driven 4WD (no internal differential) part-time 2-speed transfer case built by Borg-Warner with a fixed front yoke output on the L side & a magnesium-alloy case. It replaced the NP 208F & BW 1342, and was built in several configurations manual-shift/ESOF; with PTO (Aluminum front case)/without; with/without speedo gear bore; fixed/slip rear output; yoke/companion flange fixed rear output. It was used in 1/2-ton pickups & Broncos, and F350s w/PSTD, so it's a VERY strong box.
Byte  a group of bits (usually 8 or 16, though modern PCs are 32- or 64-bit) interpreted & processed as a single value. A numeric "word".
C  1) Chemical symbol for Carbon; 2) fuel code for CNG.
C    Celsius (Degrees)
C.I.D. Cubic inch displacement
Cab or Cabin  The passenger compartment of any vehicle or equipment; cab usually refers to trucks & equipment to distinguish from the detached cargo bed or working appendages; cabin usually to cars & SUVs to distinguish from the integral engine bay &/or cargo trunk, but not from an integral interior or convertible cargo bed (wagon bodies).
CAC  Charge Air Cooler. Formerly known as Intercooler. A device which lowers the temperature of pressurized intake air. 
CAFE  Corporate Average Fuel Economy. A set of federal requirements and regulations which govern fuel economy standards for all motor vehicles produced by one corporate entity. 
California Air Resources Board (CARB)  a governing body of California which establishes air pollution laws.
Camshaft  A shaft on which phased cams are cut or mounted. The cams regulate the opening and closing of the intake and exhaust valves in the head(s). See also OHC, OHV, VVT.
Camshaft Position (CMP)  A sensor or signal which indicates camshaft position.
CAN    Controller Area Network
Canister (Carbon or Charcoal)  An evaporative emissions system component which contains activated charcoal which absorbs fuel vapors and holds them until the vapors can be purged into the intake to be burned in the engine.
Canister Purge (CANP)  A circuit or solenoid valve which controls airflow through the carbon canister into the intake manifold.
Canister Vent (CV or CANVNT)  A circuit or solenoid valve which controls airflow between the carbon canister and the atmosphere.
CANP    Canister Purge
carb Carburetor
Carb  (slang) Carburetor
CARB    California Air Resources Board
Cardan Joint  A type of universal joint consisting of 2 shafts at right angles connecting 2 yokes. AKA Hooks Joint
Cardone  An aftermarket parts remanufacturer (A1 Cardone).
CAS    Crank Angle Sensor
Cascade Failure  a progressive (and usually catastrophic) failure sequence, beginning with a single (usually minor) failure that triggers several more, each which may trigger several more, and so on.
Case Ground (CSE GND)  PCM case ground circuit or terminal.
CAT Catalytic converter
CAT  Catalytic Converter
Catalytic Convertor  An in-line exhaust system device used to reduce the level of engine exhaust emissions by the use of catalysts (chemicals which cause chemical reactions without being consumed in those reactions). Most catalysts are deactivated by Lead, which is why unleaded fuel was introduced. Some cause HC to be oxidized; some cause NOx to be reduced; some convert other pollutants into non-toxic compounds.
CB    Circuit Breaker
CBD    Closed Bowl Distributor
CC Cruise control
CC  1) cubic centimeter; 2) the process of measuring the precise volume of a cylinder head by draining water from a graduated cylinder into the combustion chamber, so called because most graduated cylinders are graduated in ccs.
CC    cubic centimeter
CCA Cold cranking amps
CCC    Computer Command Control
CCD    Computer Controlled Dwell
CCM  Comprehensive Component Monitor.
CCOT    Cycling Clutch Orifice Tube
CCS, C.C.S. Controlled combustion system
CCW    Counterclockwise
CD  1) Compact Disc - any of several types of 5 inch optical medium for audio in the CDA format, or video in the VCD, SVCD, DVD, DVD-DL, HDDVD, or BD formats, or for data in any digital format; 2) Coil Driver. 
CD4E  CD class vehicle, 4 speed, Electronic transmission.
CDI    Capacitor Discharge Ignition
CEC    Computerized Engine Control
CEC, C.E.C. Combined emission control
Centralized Testing Facility  A state government inspection/maintenance (IM) and safety station. 
CFM Cubic Feet per Minute
Chain(s)  1) A steel recovery chain; 2) tire chains; 3) a timing or transfer case chain.
Chase (Threads)  to repair machine threads by reforming or recutting with a tap, die, file, or rethreading tools; to clean machine threads by running mating threads over them while rinsing with oil.
Chassis  The working components of a vehicle, not including the body or its wiring.
Check Engine Light (CEL)  A warning light used to indicate a fault has been detected either in the engine, transmission, or emissions systems. Some can be triggered to flash out fault codes. AKA MIL.
CID    Cubic Inch Displacement
Circuit  1) A complete electrical path or channel, usually including the source of electrical energy; 2) the electrical path (wire) between two or more components; 3) an analogous condouit for fluids, as in hydraulic or pneumatic controls.
Citizens Band (CB)  1) A band of low radio frequencies deregulated by the FCC for civilian use; 2) A radio which operates in that band.
CKP    Crankshaft Position Sensor
Clean Tach Output (CTO)  A signal or circuit used to drive the instrument panel tachometer.
Closed Loop (CL)  An operating mode which manages outputs based on sensor feedback. Contrast Open Loop.
Clutch  A mechanism for connecting & disconnecting 2 rotating assemblies or shafts, such as an engine & transmission, or a pulley & compressor.
CM    Centimeter
CMP    Camshaft Position Sensor
CMVSS  Canadian Motor Vehicle Safety Standards.
CNG  Compressed Natural Gas. See Natural Gas. Compare LNG; contrast LPG.
CO  Carbon Monoxide.
CO    Carbon Monoxide
CO2  Carbon Dioxide.
CO2    Carbon Dioxide
Coast Clutch Solenoid (CCS)  Controls the application and release of the coast clutch in the transmission.
Coil  1) A device consisting of conductors wrapped around a magnetizable core, often used to increase the voltage in a spark ignition system; 2) a coil spring.
Cold Soak  Time given to a vehicle to sit at a low temperature (typically below 68° F / 20° C) until the temperature of external and internal components stabilize.
Cold-Rolled or Cold-Formed  A metal part which has been reshaped (OTHER than by cutting or hammering) below its eutectic temperature, resulting in internal stresses & work-hardening. Contrast Hot-Rolled, Hot-Formed, Annealed.
Combo  a small module attached to '87-91 truck instrument clusters which triggers an EMISSIONS warning light. It serves no purpose since no supplier (including Ford) ever made the parts it was intended to indicate were due for replacement.
COMP Compressor
Compression Ratio (CR)  the ratio of the volume of the compression chamber to that PLUS the piston's displacement. Most engines are built for approximately 81; high-performance engines are around 91; diesels are above 111. Deposits in the combustion chamber or on the pistons will raise the CR, sometimes to levels that will damage the engine. Com
Compression Test  a basic procedure for checking the general condition of an engine by measuring each cylinder's ability to create pressure, and then comparing those numbers to each other (NOT to any fixed standard). Most engines are considered passing if the lowest cylinder is >75% of the highest, and adjacent cylinders are within 20%. Initially, the test is performed with the cyinders empty (dry); if there's a failing cylinder, it is retested with engine oil added (wet). Compare Leakdown Test.
Compressor  A pump that takes in relatively low-pressure gas and releases very high-pressure gas at low flow rates, usually to be condensed into a liquid after passing through an heat exchanger (intercooler or condenser). 
Computed Timing  The total spark advance in degrees before top dead center; equal to base timing plus/minus an additional factor calculated by the PCM based on input from a number of sensors.
Computer Controlled Dwell (CCD)  A variant of the TFI-IV ignition system in which the EEC processes several signals into the SPOUT, and the ICM uses both the rising & falling edges of that signal to control both ignition timing AND dwell. Contrast Push-Start.
Constant Control Relay Module (CCRM)  A relay module that provides on-off control of various EEC components.
Cont.    Continued
Continuous Duty  In operation without interruption. Some devices (usually electrical relays, solenoids, & motors) are designed only for intermittent use; others can tolerate constant on-time, without overheating or wearing out prematurely.
Continuous Memory (CM or CONT)  The portion of KAM used to store DTCs generated during the Continuous Memory Self-Test.
Continuous Memory Self-Test  A continuous test of the EEC system conducted by the PCM whenever it is operating.
Control  A means or device which directs and regulates a process, machine, apparatus, or system.
CONV    Convertible
Conv, conv Convertible
Coolant  A fluid used for heat transfer; typically water. Coolants usually contain additives such as rust inhibitors and antifreeze/antiboil agents like ethylene glycol. They may also contain bittering agents to discourage consumption since most additives are toxic and sweet.
COP    Coil On Plug Ignition
copo, COPO, C.O.P.O Central office production ordered
CP    Canister Purge
cp, cpe, Cpe Coupe
CPI    Central Port Injection
CPP  Clutch Pedal Position sensor, switch, or circuit.
CPU    Central Processing Unit
CQIS  Common Quality Indicator System.
crank Crankshaft
Crankshaft  The part of an engine which converts the reciprocating motion of the pistons to rotary motion, and connects to the transmission. It also usually drives the engine accessories.
Crankshaft Position (CKP)  A sensor, signal, or circuit which indicates crankshaft position.
Cryogenic  Any process involving temperatures significantly below 0F; often involving liquid Nitrogen or dry ice.
CSSA    Cold Start Spark Advance
CSSH    Cold Start Spark Hold
CST Custom Sport Truck
CTS    Coolant Temperature Sensor
CTVS    Choke Thermal Vacuum Switch
cu, cu.in, C.I. Cubic inch
Cu. In.    Cubic Inch
Curb Idle  The idle rpm when the engine is at normal steady-state operating conditions.
Curb weight Weight of empty vehicle ready to drive. It is the shipping weight plus weight of gasoline and antifreeze.
CV    Check Valve or Constant Velocity
CVC    Constant Vacuum Control
CVCC    Controlled Vortex Combustion Chamber
CVR    Control Vacuum Regulator
CVVT  Continuous Variable Valve Timing
CW    Clockwise
CYL or Cyl.    Cylinder
Cyl, cyl Cylinder
Cylinder Head Temperature (CHT)  A sensor, signal, or circuit which indicates the temperature of the engine cylinder head.
Cylinder Identification (CID)  A sensor, signal, or circuit which provides crankshaft or camshaft position information for fuel injection synchronization.
D  1) Drain (ammeter or Alt gauge) indicates the alternator is supplying LESS current than the vehicle is consuming, so the battery is discharging; 2) combustion code for Diesel Cycle; 3) fuel code for Diesel
D    Drive
D.O.T. Department of transportation
Daily Driver (DD)  A vehicle comfortable & reliable enough to be used every day for commuting, but which isn't necessarily suited to work (hauling/towing) or play (off-roading). Compare Grocery-Getter, Weekend Warrior.
Dashpot  A vacuum diaphragm that controls the throttle stop &/or closing speed to assist with idle control and reduce run-on (carburetor/vacuum)
Data  General term for information, usually that has been simplified into numbers, letters, or symbols.
Data Link Connector (DLC)  J1962 or EEC-IV connector providing access and/or control of the vehicle information, operating conditions, and diagnostic information.
Data Output Line (DOL)  A circuit that sends certain information from the PCM to the instrument cluster.
Data Positive or Negative (DATA+ or DATA-)  Circuits that carry data to the DLC, Message Center, or VCRM.
DATA+ or DATA-  Data Positive or Negative.
Daytime Running Lamps (DRL)  A system that keeps the vehicle headlamps on at all times (though often at reduced power & without marker lamps) while the vehicle is operating.
Db  Decibel, a logarithmic measurment of sound intensity.
DB  Dark Blue wire or vacuum line.
dB    Decibels
DC  1) Direct Current. Electric current flowing in one direction, as from a battery; 2) Duty Cycle. The ratio of ON time versus the sum of ON & OFF times, expressed in percent. 
DC    Direct Current Or Discharge
DCL  Data Communication Link. See Data Link Connector.
DD  1) Direct Drive; 2) Drunk Driving; 3) Daily Driver.
DDD    Dual Diaphragm Distributor
DDM  Driver's Door Module - an electronic component that controls systems related to the driver's door, including PL, PW, OTD, KE, RKE.
Decimal  a common numbering system using ten possible characters in each digit, based on human fingers. "Deci-" means ten.
DEF  1) Defroster; 2) Diesel Emissions Fluid  32.5% urea + 67.5% deionized water injected into diesel exhaust to reduce NOx emissions.
Def.    Defrost
DEFI    Digital Electronic Fuel Injection
Defog.    Defogger
Defroster (DEF)  An electrically heated device designed to remove ice, frost or snow from the rear window of the vehicle.
DERM    Diagnostic Energy Reserve Module
Detonation  See Knock.
Detroit Locker  An aftermarket locking differential famous for reliability & robustness, now manufactured by Eaton.
DFI    Digital Fuel Injection
DFR  Dual-Function Reservoir 
DFS    Deceleration Fuel Shutoff
DG  Dark Green wire or vacuum line.
DI  1) Distributor Ignition, see TFI-IV; 2) Direct Injection. 
Diag.    Diagnostic
Diagnostic Test Mode (DTM)  A level of capability in an On-Board Diagnostic (OBD) system. This may include different functional states to observe signals, a base level to read Diagnostic Trouble Codes, a monitor level which includes information on signal levels, bi-directional control with on/off board aids, and the ability to interface with remote diagnosis.
Diagnostic Trouble Code (DTC)  An alpha/numeric identifier for a fault condition identified by the On-Board Diagnostic System.
Diags  1) Diagonal wire cutting pliers, often misspelled "dykes" or "dikes"; 2) Diagnostics.
Dial Indicator  A calibrated instrument for measuring very small linear movement; usually less than 1" by thousandths. They are often used to measure cam lobes, concentricity of crankshaft journals, bends in rotating shafts, endplay in shafts, backlash in gears, runout in brakes, and slop in spherical joints. They can be mounted by fastener, magnet, clamp, or other means.
DIC    Driver Information Center
Die  A tool for cutting external threads onto a shaft or rod. Contrast Tap, Thread Chaser, Thread File.
Dielectric  Electrically insulating.
Dielectric Grease  Silicone grease used on small electrical terminals to block Oxygen & moisture in order to improve the durability of the connection. On larger terminals (like battery posts), the larger surface area can allow the grease's high film strenght to break or severely inhibit the electrical connection.
Diesel  1. A german scientist who invented a simple & reliable engine which can run efficiently on very low-grade fuel oil; 2. An engine which operates on the Diesel (2-stroke or 4-stroke) cycle; 3. The fuel for such engines. Untaxed diesel fuel (for agricultural use) in the US has a dye added so that inspectors can tell if it was used in taxable vehicles.
Dieseling  See Knock.
DIFF Differential
Differential (Diff)  A mechanism for dividing the engine's power between 2 shafts, most often between the 2 axleshafts within an axle or transaxle, but also sometimes between 2 driveshafts within an AWD transfer case. Most are "open", meaning the mechanism is allowed to work without limitation, which results in the input torque being split inversely to the output resistance (the tire with the least traction gets the most torque). Others may contain clutches (limited slip) or more complex mechanisms (torque-biasing) to restrict the division of torque and aid in traction. Contrast Spool, Lincoln-Locker, 4WD.
Differential Pressure  The pressure difference between two regions, such as between the intake manifold and the atmospheric pressures.
Differential Pressure Feedback EGR (DPFE)  An EGR system or its primary sensor that monitors EGR pressure across a remote orifice to control EGR flow. AKA Dual Pressure Feedback EGR
Digital  1) An electrical signal that is stepped among certain possible values within the voltage limits of the signal; 2) a display capable of only certain preset values/elements occurring only in certain positions; 3) controls which process information by switching the current or voltage through steps. Contrast Analog, Binary, Decimal, Hexadecimal.
Digital MultiMeter (DMM)  A handheld tool with a digital display for measuring various characteristics of electrical/electronic circuits & components. Digital meters require less current from the circuit being tested and produce more accurate & precise readings. They also generally have more features and cost far less than older meters. Contrast Analog Meter.
Digital Transmission Range sensor (DTR or TR)  A sensor, signal, or circuit which indicates the selected modes of the transmission. It may be used for PCM control of shifting, cruise &/or starter interrupt. AKA MLP, MLPS, PNP, NSS.
Digital Volt-Ohm Meter (DVOM)  A handheld tool with a digital display for measuring voltage or resistance characteristics of electrical/electronic circuits & components. See DMM.
Dikes  See Diags.
Diode  an electronic component that allows current to flow only in 1 direction along a circuit, and also creates a voltage drop (typically ~0.7VDC). When polarity is reversed, the voltage drop goes above 100VDC until it reaches the semiconductor's breakdown voltage. They are commonly used to drain inductance spikes across solenoid or relay coils; to convert AC into rough DC (inside alternators & transformers); to prevent semi-independent circuits from interfering with each other (like a dome light & cargo light); and to create constant smooth voltage for delicate circuits (like Zener diodes in a power supply). Some emit light (LED) and are becoming more popular as high-efficiency long-life light sources. See Light-Emitting Diode.
Direct Injection (DI)  A cylinder head design in which the fuel injector pintle is within the combustion chamber.
Direct-Replacement  Parts engineered to be equivalent (in fit & performance, if not appearance) to OE parts, but produced by non-OEM.
DIS    Distributorless Ignition System
DIS, D.I.S. Distributorless ignition system
Disk Brakes  A braking system based on a 2-sided brake rotor with a pad wearing against each side. The pads are compressed against the rotor by a caliper (usually hydraulic), creating a braking force on the rotating hub. They are less complex than drum brakes, and are less affected by extended use, fording, or high speed. See also Cross-drilled Rotor, Slotted Rotor, Drum-in-Hat. Contrast Drum Brakes.
Dissolved Gas Test  A quick test to detect block & head cracks by checking for exhaust gases in the coolant system. A squeeze bulb is used to draw air from the coolant system through a special chemical which changes color (usually blue to yellow) if exhaust is present. AKA Block Test.
DIST    Distribution
DIST, dist Distributot
Distributor  A mechanical device designed to switch a high voltage secondary circuit from an ignition coil to spark plugs in the proper firing sequence.
Distributor Ignition (DI)  A system in which the ignition coil secondary circuit is switched by a rotating mechanism in proper sequence to various spark plugs.
DLC    Data Link Connector
DM  fuel code for Bi-Fuel, Diesel/Methanol 
DMM  Digital MultiMeter. Compare DVOM. Contrast Analog Meter.
DMM  Digital Multi Meter
DOHC  Dual Overhead Cam.
DOHC    Double Overhead Cam
DOHC, D.O.H.C. Double overhead cam
DOL  Data Output Line.
Door Jamb Sticker  See Safety Certification Label.
DOT  Department of Transportation. A federal office which oversees (among MANY other things) roads & motor vehicles.
DOT    Department of Transportation
Double Cardan joint  an assembly of 2 cross-type U-joints linked by a very short coupling with a mechanism between them to hold the coupling at exactly 1/2 the total flex angle across the assembly. It provides near-constant angular velocity through the joint, and allows nearly double the flex angle of a single cardan joint.
Double Clutch  Releasing the clutch pedal suddenly to launch the vehicle, then pressing it to let the engine rev up again, and releasing a second time. With the correct engine/vehicle combination, it can reduce takeoff time by using the engine's momentum in addition to its power to get the vehicle moving. Contrast Speed Shift.
Double Hex  A style of fastener & matching tool with 12 120° points. Contrast Triple Square.
DPFE or DPFEGR  Differential (Dual) Pressure Feedback EGR. Compare PFE, EEGR, EVP.
dr Door
Drag Link  A steering link that directly joins the steering knuckles.
DRB II    Diagnostic Readout Box
DRI  Deposit Resistant Injector. A fuel injector designed to prevent buildup of carbon and other unwanted deposits used since the mid-80s.
Drift  1) A solid shaft tool used with a hammer to drive other objects, such as pins, often confused with "Punch"; 2) A driving technique involving sliding the rear wheels continuously sideways on pavement through an extended turn, purely for its dramatic effect. Contrast Fish-Tail.
Drilled Rotor  See Cross-drilled Rotor. 
Drive Cycle  A long process during which a vehicle is operated in most normal driving states, but in a specific order for a specific time each, and with certain states repeated. Normal driving will eventually produce a drive cycle, but it can take months, depending on the driver, the weather, the traffic, and the roads. Certain emissions monitors require a drive cycle before they can reset after codes are cleared.
Driveability  A classification of vehicle concerns, including engine performance, transmission behavior, and drivetrain harshness.
Driveline  1) See Drivetrain, 2) See Driveshaft.
Driveshaft  A shaft connecting a transmission or transfer case to an axle or differential. It is usually tubular, either steel, Aluminum, Aluminum-Metal Matrix (AMMX), or composite. It usually includes at least 1 U-joint, CV joint, or rubber coupling disk at each end, & a slip joint (to allow for compression & extension). For longer distances, an intermediate joint & carrier bearing may be used. 
Drivetrain  The collection of parts within a vehicle that cause it to move, including the engine, transmission, driveshaft, & drive axle. AKA Driveline, Powertrain.
DRL  Daytime Running Lamps.
Drum Brakes  A braking system based on a wide cast-iron hoop with a thin plate on one side surrounding 1 or 2 shoes covered in friction material, which are themselves attached to a large plate on the suspension (usually a solid axle), enclosing the entire mechanism. The shoes are spread against the hoop's inner surface either by a hydraulic slave (wheel) cylinder, or by a scissor mechanism, or by a lever mechanism, and usually also by an adjusting mechanism (usually automatic). See also Drum-in-Hat. Contrast Disk Brakes.
Drum-in-Hat  A brake system combining a small drum brake (usually only for emergency/parking use) inside the rotor of a disk brake (usually on the rear axle). See Disk Brakes, Drum Brakes.
D'shaft  Driveshaft.
DTC  Diagnostic Trouble Code.
DTC    Diagnostic Trouble Code
DTM  Diagnostic Test Mode.
DTR  Digital Transmission Range sensor.
Dual Exhaust  an system that provides 2 equal-sized paths for the engine exhaust from the manifolds (or headers) to the tailpipes. "True" dual exhaust has no connection between the 2 pipes, which is less efficient than a well-engineered crossover.
Dual Overhead Cam (DOHC)  An engine configuration that uses two camshafts in each cylinder head, positioned above the valves.
Dual-Function Reservoir (DFR)  A pressure-operated fuel tank switching valve with an integral reservoir which may contain a filter. It is only used on dual-tank Ford trucks from '84-89 and is notoriously unreliable.
Duckbill  The common term for a specific style of plastic quick-connector used on some fuel line & heater hose fittings. Compare Garter Spring, hairpin.
DUI.  1) Davis Unified Ignition - an ignition system common on '80-00 GM vehicles, and a popular modification on many others. It involves a distributor with integrated pickup, advance, coil, & module requiring as few as 1 wire to work. 2) Driving Under the Influence of drugs or alcohol, a.k.a. DWI, DD.
Dust Cap  The outboard cover for a hub. Some include the knob or dial for manual hub locks on 4WD vehicles.
DVOM  Digital Volt-Ohm Meter. Compare DMM.
DVOM    Digital Volt Ohmmeter
DWI  Driving While Intoxicated.
Dye  A chemical additive used for visual identification or diagnosis, often fluorescent (UV).
Dykes  See Diags.
Dynamic  Moving/changing. Contrast Static.
E  1) combustion code for Electric; 2) fuel code for Ethanol; 3) EGR vacuum supply port (carburetor/vacuum)
E.F.I. Electronic Fuel Injection
E4OD  Electronic 4-speed Overdrive automatic transmission based on the C6. Renamed 4R100; one of the strongest, longest, & heaviest automatic transmissions ever put in a light truck. Models built before 1995 developed a poor reputation.
E85  Fuel containing 85% ethanol (ethyl alcohol). Pure ethanol is the alcohol which is the intoxicating agent in liquor, beer and wine. It is distilled from the fermentation of plants such as field corn and sugar cane. A denaturant that imparts a bad taste is added to ethanol to preclude consumption. Up to 5% hydrocarbons (such as unleaded gasoline) is a typical denaturant. The resulting denatured ethanol is designated Ed100 when used as a feedstock for motor fuels. Fuel ethanol (Ed85) is then made by adding 15% more unleaded gasoline. The resulting fuel also has a higher octane rating than unleaded regular gasoline, allowing engine designs with higher compression and corresponding greater engine efficiency and performance (power). Winter blends may contain up to 25% unleaded gasoline (plus the denaturant) to enhance cold engine starts, hence the sometimes used Ed85-Ed75 designation. Severely cold weather may require additional measures for reliable starting. Ethanol is more chemically active than gasoline. It corrodes some metals and may cause some plastic and rubber components to swell, break down, or become brittle and crack, especially when mixed with gasoline. Special materials and procedures are used with Ethanol FFVs. Ethanol has less energy per gallon than gasoline, so fuel economy in miles per gallon will decrease as the percentage of ethanol goes up. However, the decrease is not as severe as with methanol. Flexible fuel vehicles using fuel ethanol also have lower exhaust emissions than comparable gasoline vehicles.
ea Each
EACV    Electronic Air Control Valve
EAIR  Electric Secondary Air Injection.
EAP  Electric Air Pump.
eB  early Bronco ('66-77).
EB  1) Eddie Bauer; 2) (slang) early Bronco.
EBCM  Electronic Brake Control Module
EBL    Electronic Back Light
EBM    Electronic Body Module
ECA    Electronic Control Assembly
ECC  Electronic Control Computer. See EEC.
ECM Electronic control module
ECM  Electronic Control Module. See EEC.
ECM    Engine Control Module
ECT  Engine Coolant Temperature.
ECT    Engine Coolant Temperature
ECU  Electronic Control Unit. See EEC.
ECU    Electronic Control Unit
Eddie Bauer  The most-luxurious trim level offered on Ford trucks from '85-96. Later models included matching leather luggage.
EDIS    Electronic Distributorless Ignition System
EDP Electro Deposted Primer
EEC  Electronic Engine Control. AKA ECC, ECM, ECU, MCU, PCM, "brain", "computer", "controller".
EEC    Electronic Engine Control
EEC-IV  Ford's fourth-generation EEC system; its first to incorporate on-board diagnostics (OBD) & memory to store diagnostic trouble codes (DTCs). Their chips are soldered to their boards (meaning they can't be removed to change performance characteristics like some other manufacturers), but later versions include flash-programmable memory (EEPROM).
EECS    Evaporative Emission Control System
EEC-V  Ford's fifth-generation EEC system, which incorporates the industry-standard OBD-II system.
EEGR  Electronic EGR Valve; a motor-driven EGR with an integral position sensor.
EEPROM  Flash Electrically Erasable Programmable Read Only Memory.
EEPROM    Electronically Erasable Programmable Read Only Memory
EFC  Electronic Fuel Control
EFCA  Electronic Fuel Control Assembly
EFE    Early Fuel Evaporation
EFE, E.F.E. Early fuel evaporation
EFI    Electronic Fuel Injection
EFT  Engine Fuel Temperature.
EGO  Exhaust Gas Oxygen sensor, signal, or circuit. An early version of a HEGO, without the heater.
EGO    Exhaust Gas Oxygen Sensor
EGR  Exhaust Gas Recirculation.
EGR    Exhaust Gas Recirculation
EGR Vacuum Regulator (EVR)  A solenoid vacuum valve which controls vacuum to the EGR valve by a duty cycle (pulse) signal from the PCM. This, in turn, regulates EGR flow into the intake manifold. The EVR switches its output (to the EGR) between vent and manifold vacuum (through a reservoir).
EGR Valve Position (EVP)  A sensor, signal, or circuit which reports how far the EGR valve has opened to the EEC. It mounts directly to the EGR and uses a pushrod to measure how far the diaphragm has lifted the pintle. Newer EGR systems don't use this sensor. Contrast EEGR, PFE, DPFEGR.
EGRPS  EGR Valve Position Sensor
EGRT  EGR Valve Temperature Sensor.
EGRT    EGR Temperature
EGT  Exhaust Gas Temperature
EGT    Exhaust Gas Temperature
EI  Electronic Ignition.
EI    Electronic Ignition
Electric Air Pump (EAP)  An electric pump used in EAIR systems.
Electric Secondary Air Injection (EAIR)  A pump-driven system for providing secondary air using an electric air pump.
Electronic Distributorless Ignition System (EDIS)  A system using an independent ignition module and one or 2 coil packs. AKA Integrated Ignition.
Electronic Engine Control (EEC)  The system or module that provides electronic control of engine (and often transmission) operation. AKA ECC, ECM, ECU, MCU, PCM, "brain", "computer", "controller". Contrast BCM, DDM, GEM, LCM.
Electronic Ignition (EI)  A system in which the ignition coil secondary circuit is dedicated to specific spark plugs without the use of a distributor. Ford has two types of EI systems, integrated EI and EI. EI is only used on the 3.0L Windstar and has a standalone Ignition Control Module (ICM). The Integrated Electronic Ignition (EI) System consists of a crankshaft position (CKP) sensor, coil pack(s), connecting wiring, and PCM. The Coil On Plug (COP) Integrated EI System uses a separate coil for each spark plug and each coil is mounted directly onto the plug. The COP Integrated EI System eliminates the need for spark plug wires but does require input from the camshaft position (CMP) sensor.
Electronic Pressure Control (EPC)  A solenoid valve, signal, or circuit which controls line pressure in the transmission.
Electronic Shift-On-the-Fly (ESOF)  A system used to operate the transfer case of a 4WD or AWD vehicle while it is in motion.
Electronic Variable Orifice Steering (EVO)  A system or solenoid valve which adjusts the level of assistance provided by the power steering system.
E-Locker  An aftermarket electronically-selectable-locking differential produced by Eaton.
EMI  Electromagnetic Interference. Usually caused by ignition voltage spikes, solenoids, relay operation or noisy generator contacts.
EMI    Electromagnetic Interference
EMR    Electronic Module Retard
EMW  Emissions Maintenance Warning module. A small module attached to certain '87-91 instrument clusters which can be safely deleted. Compare Combo, IMS. AKA EUL.
Endo  An end-over-end roll.
Engine  A machine designed to convert thermal energy (typically derived from chemical energy in fuel) into mechanical energy to produce force or motion.
Engine Coolant Temperature (ECT)  A sensor, signal, or circuit which indicates the temperature of the engine coolant. It is typically installed in the heater core circuit, which is unaffected by the thermostat.
Engine Fuel Temperature (EFT)  A sensor, signal, or circuit which indicates the temperature of the fuel in the fuel rail.
Engine RPM (RPM)  A signal or circuit which indicates engine rpm.
Engine RPM/Vehicle Speed Limiter  A strategy to prevent damage to the powertrain. The powertrain control module (PCM) will disable some or all of the fuel injectors whenever an engine rpm or vehicle overspeed condition is detected. The vehicle will exhibit a rough running engine condition, and the PCM will store a Continuous Memory DTC P1270. Once the operator reduces the excessive speed, the engine will return to the normal operating mode. No repair is required. However, the technician should clear the PCM and inform the operator of the reason for the DTC. Excessive wheel slippage may be caused by sand, gravel, rain, mud, snow, ice, etc. or excessive and sudden increase in rpm while in NEUTRAL or while driving.
EOBD    European Onboard Diagnostics
EOL  End Of Line. A system designed specifically for use at assembly plants to make sure all new vehicles perform to design specifications.
EOS  Exhaust Oxygen Sensor or Engine Oil Suppliment
EP  Extreme Pressure; a rating for chassis grease.
EPA  Environmental Protection Agency; a government agency which sets & enforces emissions standards in the US.
EPC  Electronic Pressure Control.
EPOS  EGR Valve Position Sensor
Epoxy  A plastic formed by mixing several liquid or gel chemicals, which then harden. Most do not require air to cure, and will cure over a wide temperature range. Heat is usually produced by the curing process. Epoxies are commonly used as adhesives, sealants, paints, and structural repairs (JB Weld) because they are robust & durable.
EPROM    Erasable Programmable Read Only Memory
E-Ring  A hardened spring steel clip shaped vaguely like an "E"; more like a "C", but with a tab in the center. It is used on shafts & operating rods.
ESA    Electronic Spark Advance
ESC    Electronic Spark Control
Escutcheon, escutcheon plate A trim plate or a shield surrounding a moving part like the windshield wiper shaft or the trim piece around a radio knob, etc.
ESOF  Electronic Shift-On-the-Fly.
EST    Electronic Spark Timing
Estate  See Wagon-Body.
ETC    Electronic Throttle Control
Ethanol  Grain alcohol; C2H5OH. An inexpensive fuel additive used to reduce cost and emissions. Blends containing more than ~15% ethanol require special engine management & fuel system materials. See E85.
Ethylene Glycol  The most common antifreeze/antiboil agent in automotive coolant. It tastes sweet, but is extremely poisonous; attaching to the liver, it prevents normal toxins from being removed from the blood.
EUL  See EMW.
EVAP  Evaporative Emission system.
EVAP    Evaporative Emission System
Evaporative Emission (EVAP)  A system to prevent fuel or other hydrocarbon vapors from escaping into the atmosphere. Typically includes a charcoal canister to store fuel vapors, a rollover valve on the fuel tank to prevent liquid fuel from entering the system, various airflow control solenoid valves, & the PCV system.
EVIC    Electronic Vehicle Information Center
EVO  Electronic Variable Orifice.
EVP  EGR Valve Position
EVR  EGR Vacuum Regulator (AKA Exhaust Valve Regulator).
EWP  Electric Water Pump.
Exciter Ring  See Tone Ring.
EXH HCV  Exhaust Heat Control Valve (carburetor/vacuum)
Exhaust Gas Recirculation (EGR)  A system which reduces NOx emissions levels by adding exhaust gas to the incoming air/fuel mixture, OR the valve used to regulate the flow of exhaust gas. The inert gas reduces combustion chamber temperatures, which not only reduce the formation of NOx, but also reduces the tendency to burn through Aluminum/alloy pistons.
Exo-Cage  An external cage designed to protect a vehicle's body when off-roading. Most are primarily cosmetic, and not actually strong enough to work in an off-road rollover or on-road collision. Contrast Family Cage; Nerf Bar; Rock Slider; Roll Bar; Roll Cage; Step Bar.
F  Front
F    Fahrenheit
F/B    Fuse Block
F4E  F Level (119 lb-ft) 4 speed Electronic transmission.
Fabricated  1) assembled, as opposed to being a single piece; 2) welded-together, as opposed to being stamped or machined in 1 piece; 3) created locally from raw or common materials, as opposed to being mass-produced on a factory assembly line; 4) crude, as opposed to being professionally designed & built to modern standards.
Fail-Safe Cooling Strategy (FSC)  A strategy activated by the PCM only in the event that an overheating condition has been identified. This strategy provides engine temperature control when the cylinder head temperature exceeds certain limits. The cylinder head temperature is measured by the CHT sensor. Not all vehicles equipped with a CHT sensor will have the fail-safe cooling strategy. A cooling system failure such as low coolant, electric cooling fan failure, or coolant loss could cause an overheating condition. As a result, damage to major engine components could occur. Along with a CHT sensor, the fail-safe cooling strategy is used to prevent damage by allowing air cooling of the engine. This strategy allows the vehicle to be driven safely for a short time with some loss of performance when a overheat condition exist. Engine temperature is controlled by varying and alternating the number of disabled fuel injectors. This allows all cylinders to cool. When the fuel injectors are disabled, their respective cylinders work as air pumps, and this air is used to cool the cylinders. The more fuel injectors that are disabled, the cooler the engine runs, but the engine has less power. A wide open throttle (WOT) delay is incorporated if the CHT temperature is exceeded during WOT operation. At WOT, the injectors will function for a limited amount of time allowing the customer to complete a passing maneuver. Before injectors are disabled, the fail-safe cooling strategy alerts the operator to a cooling system problem by moving the instrument cluster temperature gauge to the hot zone and a PCM DTC P1285 is set. Depending on the vehicle, other indicators, such as an audible chime or warning lamp, can be used to alert the operator of fail-safe cooling. If overheating continues, the strategy begins to disable the fuel injectors, a DTC P1299 is stored in the PCM memory, and a malfunction indicator light (MIL) (either CHECK ENGINE or SERVICE ENGINE SOON), comes on. If the overheating condition continues and a critical temperature is reached, all fuel injectors are turned off and the engine is disabled.
Failure Mode Effects Management (FMEM)  An alternative vehicle operation strategy that protects vehicle function from the adverse effect of an EEC system failure.
Family Cage  a style of Roll Cage with full-height protection for rear passengers.
Fan  A device designed to supply a current of air, typically through a radiator, condenser, or transmission cooler. A fan may also have a frame, motor, wiring harness and the like. The term is typically applied to mechanisms which move air parallel to the fan's axis of rotation, and are distinguished from Blowers, which are typically centrifugal. Contrast air pump, air compressor.
Fan Control (FC)  A sensor, signal, or circuit for controlling the engine cooling fan.
FC  Fan Control.
FCIL  Fuel Cap Indicator Lamp
FCS    Fuel Control Solenoid
FDC    Fuel Deceleration Valve
FDM  Fuel Delivery Module.
FEAD  Front End Accessory Drive belt system.
Fed    Federal
Fender  The body panel above the front wheel or forward of the doors, distinguished from the Quarter Panel, which is behind the doors.
FEPS  Flash EEPROM Programming Signal. 18 volt DC signal sent by the scan tool to initiate PCM reprogramming.
FF  Flexible fuel.
FFV  Flexible Fuel Vehicle.
FI    Fuel Injection
FI, F.I. Fuel injected
FIFO  First In First Out. A stock management pattern. Contrast LIFO, LILO, FILO.
Fifth Wheel (5th Wheel)  a common heavy-duty hitch system characterized by a round tiltable horizontal receiver (the fifth wheel) on the tow vehicle (tractor) and a vertical pin on the trailer; contrast Gooseneck. It is popular in heavy truck & large RV trailer applications.
FILO  First In Last Out. A stock management pattern. Contrast LIFO, LILO, FIFO.
Finite-Element Analysis  An engineering design process pioneered by Ford in the late 60s and first applied to a production vehicle on the Falcon Wagon. A physical part (which has nearly infinite elements in the forms of crystals &/or molecules) is simulated mathematically by a model containing a finite (MUCH smaller) number of elements, represented by triangles arranged as a web or wireform. The behavior of the part can then be calculated at various temperatures & load conditions to determine which elements are critical & which are expendable, thereby reducing the size & weight of the part, without reducing its strength, durability, or reliability. It is now an indispensible tool for nearly every engineering & physics discipline, and has altered industry almost as profoundly & abruptly as Ford's seminal contribution,  the production line.
FIPK  A popular aftermarket Open-Element air filter system by K&N.
FIPL    Fuel Injector Pump Lever
Firewall  The body panel between the engine bay & the passenger compartment.
Fish-Tail  A driving maneuver (often accidental) accomlished by accelerating vigorously but briefly during a short turn that results in the back end of the vehicle whipping sideways, like a fish's tail.
Fixed Yoke/Flange  A non-moving connection between a splined shaft (usually the output shaft of a transmission or transfer case) and a U-joint in a driveshaft. Broncos use a fixed yoke or flange on the t-case rear output.
Flash Electrically Erasable Programmable Read Only Memory (EEPROM)  An Integrated Circuit (IC) within the PCM. This IC contains the software code required by the PCM to control the powertrain. One feature of the EEPROM is that it can be electrically erased and then reprogrammed without removing the PCM from the vehicle. If a software change is required to the PCM, the module no longer needs to be replaced, but can be reprogrammed at the dealership through the DLC.
Flathead  1) A flathead (slotted) screw; 2) a flathead engine.
Flathead Engine  An obsolete engine design distinguished by simple cylinder heads and valves within the block.
Flathead Screw  A style of screw head using a simple, straight, central groove designed to be driven by a correspondingly simple, straight-edged tool. AKA Slotted Screw. See Screw. Contrast Phillips, Torx.
Flat-Rate or Flag-Rate  A common pay plan for automotive technicians, especially at a dealership. A comprehensive list of possible vehicle repairs is published (either by the manufacturer in the case of dealership & warranty repairs or technicians, OR by a 3rd-part company in the case of independent techs & customer-pay repairs) with specific descriptions of the tasks involved and the typical or allowable time to accomplish those tasks. Regardless of how long it actually takes the technician to complete the repair or the total cost billed to the vehicle owner, the tech is only paid for the published time. AKA "book time". Contrast "straight time" or "clock time".
Flexible Fuel (FF)  A system capable of using a variety of fuels for vehicle operation. These may include gasoline, diesel, biodiesel, ethanol, methanol, natural gas, propane, jet fuel, solar, or any combination.
Flip  A roll onto the roof either end-over-end or sideways, or a barrel roll.
Flop  A roll onto only one side (not onto the roof).
FLS    Fluid Level Sensor
FLTR  Filter (carburetor/vacuum)
Fluorescent  The physical characteristic of a substance by which it converts absorbed radiation at one frequency (usually invisible) into a visible-frequency radiation (light). Most commonly, a mercury-vapor tube generates UV radiation, which is fluoresced into white light by the powdered phosphor coating inside the tube.
FMEM  Failure Mode Effects Management.
FMX  An early medium-duty automatic transmission derived from the FX/MX. It evolved into the AOD, AODE, 4R70W, and 4R75E.
FoMoCo  An official abbreviation for Ford Motor Company, sometimes stamped into low-trim parts such as police hub caps.
Forced Induction  Any air intake system using mechanical devices to push air into the intake at higher-than-atmospheric pressure. Contrast N/A. See Turbocharger, Supercharger, Ram-Air.
Four Valve (4V)  Four valves, two intake and two exhaust, per cylinder.
Four-Cycle  (slang) See Four-Stroke Cycle.
Four-Stroke  (slang) See Four-Stroke Cycle.
Four-Stroke Cycle  An engine operating system that involve 4 strokes of each piston to complete one combustion cycle (a version of the Otto combustion cycle). On the first stroke, the piston is forced up by the crankshaft toward an open exhaust valve to expel burned fuel. Near the top of that stroke, the exhaust valve closes & the intake valve opens. On the second stroke, the piston is drawn down by the crankshaft, creating a vacuum in the cylinder which pulls fresh air (and usually gasoline) in. Near the bottom of that stroke, the intake valve closes. On the 3rd stroke, the crankshaft pushes the piston up toward a closed combustion chamber, creating pressure in the cylinder. Near the top of that stroke, diesel may be injected or a spark plug may be fired. On the fourth stroke, the burning fuel in the chamber forces the piston down, transferring power to the crankshaft. Because 3 strokes consume power for each 1 that produces power, 4-stroke engines are inherently less powerful by weight & less thermodynamically efficient than 2-strokes. But they require less maintenance & produce fewer emissions.
FP  Fuel Pump.
FPDM  Fuel Pump Driver Module.
FPM  Fuel Pump Monitor.
FPR  Fuel Pressure Regulator.
FPR VSV Fuel Pressure Regulator Vacuum Switching Valve
FPRC  Fuel Pressure Regulator Control.
FR, fr Front
Frame  The heavy structure to which all other major components of a cab-on-chassis vehicle are attached. Common types include ladder & X . Contrast Unibody, Monocoque.
Frame Horn  The end of a frame rail where something may be attached, such as a bumper.  the amount of current a 12V battery can deliver over a given time period without falling below 10V . Common time periods range from 2-10 hours, and indicate the actual amount of energy stored within a battery. Higher Ahs over shorter periods are better, and those numbers come from larger, heavier batteries. Compare CA, CCA, HCA, RC.
Freeze Frame  A block of KAM containing the vehicle operating conditions for a specific time. Typically associated with a DTC. Erasing DTCs also erases all freeze frames. They will also be erased if KAM or KAPWR fails.
Freon®  The DuPont name for R-12 CFC. See Refrigerant.
Front End Accessory Drive (FEAD)  A system of belts & pullies on the engine to transfer power from the crankshaft to various accessory devices.
FS  1) Fullsize; 2) for sale.
FSA  Field Service Action. See Recall.
FSC  Fail-Safe Cooling Strategy.
FT  1) (ft) foot (12 inches); 2) Finger-tight; 3) (slang) F*****g tight
ft, Ft Front
ft.lb.    Foot Pound
ft-lb  foot-pounds; a measure of torque (typically used for ROTATING torque, as in engine output). 1 ft-lb = 1 lbf at 1 ft from the center of rotation = 2 lbf @ 0.5' = 10 lbf @ 0.1'...
FTO  Filtered Tachometer Output; the IDM circuit for CCD TFI-IV ignition systems.
FTP  Fuel Tank Pressure.
Fuel  Any combustible substance burned to provide heat or power. Typical motor vehicle fuels include gasoline, diesel fuel, propane, CNG, LPG, ethanol, methanol, kerosene, & nitromethane. Other types of fuel include hydrogen, oxygen, hydrogen peroxide, butane, coal, wood, Uranium...
Fuel Delivery Module (FDM)  the assembly containing the fuel pump, pickup siphon, pickup screen, reservoir, shuttle valve, & level sender used in most '90-up Fords
Fuel Injector  See Injector.
Fuel Pressure Regulator (FPR)  A vacuum-operated valve on or near the fuel manifold (rail) which regulates fuel pressure from the pump to the injectors.
Fuel Pressure Regulator Control (FPRC)  A sensor, signal, or circuit which controls the fuel pressure regulator. Used primarily to provide extra fuel during cold starts.
Fuel Pump (FP)  A pump used to deliver fuel to the engine, usually submerged in the fuel tank.
Fuel Pump Driver Module (FPDM)  A module that controls an electric fuel pump in response to a pulse-code modulated (PCM) signal from the EEC.
Fuel Pump Monitor (FPM)  A sensor, signal, or circuit which monitors operation of the fuel pump.
Fuel Rich/Lean  A qualitative evaluation of air/fuel ratio relative to an ideal A/F ratio known as stoichiometry, or 14.7 1 for normal gasoline. In the EEC system, rich/lean is determined by a voltage signal from the HO2S. An excess of oxygen (lean) is indicated by an HO2S voltage of less than .4 volts; a rich condition is indicated by an HO2S voltage of greater than .6 volts.
Fuel Tank Pressure (FTP)  A sensor, signal, or circuit which indicates the internal pressure of the fuel tank and the EVAP system.
Full-Floating (FF) Axle  An axle assembly whose axleshafts bear no weight, and can therefore 'float' within the housing. Because the shafts only experience torsional stresses, it is considered stronger (less likely to break) than a Semi-Floating Axle. All steering axles are full-floating, but their outers can be semi-floating, as in some Jeeps. Most Portal Axles are full-floating. A full-floating axle can be easily identified by the presence of a spindle nut which retains the hub on the bearings, even if the axleshaft breaks.
Fullsize (FS)  a vehicle approximately 74" wide; distinguished from Midsize, Compact, Subcompact, and Heavy.
Full-Width (FW)  a part or assembly for a fullsize vehicle, but installed on a midsize or compact; usually an axle.
Fuse  An electrical connection designed to melt at a specific current draw (Amperes), thus opening (turning off) the circuit and protecting the wires from melting or burning. Installing a fuse rated higher than original defeats the purpose of the fuse since the wiring will melt before the larger fuse. Contrast Fusible Link, Circuit Breaker.
Fusible Link  A normal wire with special insulation designed to contain the heat, spark, and melted metal when the wire burns from excessive current draw. Fusible link wire is not rated in Amperes since its characteristics are less-obvious, but it is typically 4 gauges (AWG) smaller (higher number) than the circuit it protects. Although many vehicles now use MEGA or MAXI fuses where older vehicles used fusible link wire, replacing older fusible links with fuses is not recommended unless the rest of the wiring is upgraded to match the newer arrangement. Never replace a fuse with fusible link wire. In an emergency, smaller-gauge wire may be temporarily substituted for fusible link wire until an appropriate repair can be made. Contrast Fuse, Circuit Breaker.
Fusible Link Orange - 22ga. - 0.35mm
Fusible Link Gray - 20ga. - 0.5mm
Fusible Link Blue - 18ga. - 0.8mm
Fusible Link Black - 16ga. - 1.0mm
Fusible Link Gray - 14ga. - 2.0mm
Fusible Link Blue - 12ga. - 3.0mm
Fusible Link Orange - 10ga. - 5.0mm
Fusible Link Black - 8ga. - 8.0mm
FWC Front Wheel Cylinder
FWD  Front Wheel Drive. A powertrain system which delivers engine power to a differential in the front axle only. Contrast RWD, AWD, 4WD.
FWD    Front Wheel Drive
G  fuel code for Gasoline.
G    Grams
Gall  A specific type of wear between metal parts (usually rotating) in which a lack of lubricant combined with high force results in specks of liquid metal being pushed into balls which cut grooves into the parts and often lock them together.
GALS    Gallon
Gap  The distance between a spark plug's ground & center electrodes. The gap determines the voltage at which the coil fires, so too large a gap can damage the coil. Too small a gap produces a small, cold spark, which results in incomplete ignition of the fuel, low power, & high HC & CO emissions.
Garter Spring  A style of quick connection used on some fuel or A/C line fittings comprising 2 tubular fittings whose lips face each other. A coil spring fills the gap between the tubes, and interferes with the lips, preventing them from separating until the spring is pushed onto the inner (outward-facing) lip. Contrast Duckbill.
GDI    Gasoline Direct Injection
GE  fuel code for Bi-Fuel, Gasoline/Ethanol.
Gear-Drive  An aftermarket all-gear replacement for a timing chain.
GEM  Generic Electronic Module  a multi-function module used for courtesy lighting, windows & locks, chimes, etc. AKA BCM, BSM, CSM…
gen Generator
GEN    Generator
Generator (GEN)  A rotating machine designed to convert mechanical energy into electrical energy. AKA Alternator (a term trademarked by Chrysler Corporation). Early types used an external fan and remote voltage regulator; modern types use an internal fan and external or internal voltage regulator, sometimes controlled by the PCM to achieve more efficient charging & longer battery life, as well as to reduce the alternator load on the engine during peak demand. The basic generator chassis produces an AC voltage (usually around 18.5V max) which is rectified by high-current diodes to a rough DC voltage. This roughness is smoothed by the battery, which is critical to protecting modern electronics from voltage spikes which were acceptable in older vehicles. A modern vehicle should never be operated with the battery disconnected.
Glasspack  An aftermarket muffler that uses fiberglass between its outer shell & a perforated inner pipe. Externally, it looks very similar to a Cherry Bomb, and is often painted a similar red. It is popular because it fails to muffle, but is still legal in most places.
GM  1) fuel code for Bi-Fuel, Gasoline/Methanol; 2) Grand Marquis; 3) General Motors Corporation. 
Gn  Green wire or vacuum line.
GND  Ground.
GND or GRND    Ground
Gold cadmium A type of plating used on some automotive parts such as power brake boosters, fuel pumps, etc. Similar to silver cadmium only it has a gold color.  Example
Gold Plated Pins  Some engine control hardware has gold plated pins on the connectors and mating harness connectors to improve electrical stability for low-current circuits and to enhance corrosion resistance. The EEC components equipped with gold terminals will vary by vehicle application. Damaged gold terminals should only be replaced with new gold terminals.
Goose  A brief opening and closing of the throttle (Dynamic Response test).
Gooseneck  a common medium-duty hitch system characterized by a trailer tongue that arches over a pickup truck's tailgate then drops to a ball mounted to the floor of the bed; contrast Fifth Wheel. It is popular in agricultural applications.
Gov-Lock  An OE torque-biasing differential offered in GM trucks. It is very effective, but very delicate and has a history of exploding when overrevved.
GPM  Grams Per Mile; Gallons Per Minute. 
GPS  Global Positioning System. A network of geostationary satellites, or a device used to monitor signals from those satellites, and calculate its own position from that data.
GPS    Global Positioning System
Grade  1) a categorization of strength, toughness, durability, heat resistance, & corrosion resistance of fasteners. AKA Material Class in metric fasteners; 2) a long inclined driving surface.
Green State Vehicle  Formally known as California Emissions. A vehicle that is equipped with California on-board diagnostics.
Grind  A slow abrasive noise, like driving slowly on rough pavement. See NVH.
Grindbox  (slang) A manual transmission. Contrast Slushbox.
Groan  A medium steady rumbling noise, like a continuous zipper. See NVH.
Grocery-Getter (GG)  A disparaging term for a vehicle that LOOKS like an SUV but actually isn't capable of off-roading, hauling, or towing. It may also be used for a vehicle capable of those activities, but not USED for them by its owner/driver.
Ground (GND)  An electrical conductor used as a common supply for electric circuits, and with a relative zero potential, generally connected to the (-) battery terminal. Electrons (which have a negative charge) flow out of this terminal, through the ground system, to electrical & electronic components which consume their energy, through fuses & control switches, and ultimately return to the battery (+) terminal. Some vehicles & accessories use a positive-ground wiring system.
Ground Effect  1) The phenomenon by which air at relatively low pressure captured between a vehicle & the ground tends to lift the vehicle; 2) (slang) automotive bodywork added to reduce the ground effect(1), such as a front air dam or side skirts.
Ground Plane  A flat physical surface (usually the ground or the metal body of a vehicle) directly under an antenna used to reflect radio waves to or from that antenna. It must be electrically grounded to the antenna to work. The concept is almost identical to a fluorescent tube standing upright on a black surface. Without a reflector at the bottom end, ~1/2 its output would strike the surface & be lost; but with a ground-plane reflector, that energy is redirected up & out, where it can be used. The term applies primarily to CB antennae on vehicles, where the lack of a physical ground plane on one side of the antenna (due to the antenna being installed on the side of the vehicle) results in poor transmission/reception range on the side of the antenna with no ground plane.
Grounding  1) connecting one side of an electrical circuit to a common conductor (ground) to reduce the number of wires needed when many circuits have access to this common conductor (as the many circuits within a vehicle sharing the body &/or frame); 2) the unwanted mechanical connection between a noisy part & the passenger cabin of a vehicle. See NVH.
Growl  A low steady rumbling noise, like a low note on an electric guitar. See NVH.
GSS  Gear Select Solenoid
GT  Grand Touring. A style of vehicle with a better power-to-weight ratio than contemporary vehicles, making it more suited to long-distance (high-speed) travel, especially in the mountainous regions of Europe, where it can easily overtake the slower local traffic.
GVW  Gross Vehicle Weight. The maximum allowable curb weight of a vehicle.
GVW    Gross Vehicle Weight
GVWR Gross vehicle weight rating
GVWR  Gross Vehicle Weight Rating; GVW + cargo load. 
Gy  Gray wire or vacuum line.
H  combustion code for Hybrid Electric; chemical symbol for Hydrogen.
H.E.I. High Energy Ignition
H/D    Heavy Duty
H20    Water
HAC    High Altitude Compensation
Hall Effect  A process in which current is passed through a small slice of semi-conductor material at the same time as a magnetic field to produce a small voltage in the semi-conductor. Compare Magneto-Resistive sensor.
Halogen  A group of chemicals characterized by their ability to produce visible light when excited. They are often used in incandescent bulbs, but are also used in certain refrigerants for their other chemical characteristics.
Hard Fault  A fault currently detected by the system.
Hardware Limited Operating Strategy (HLOS)  A mode of operation where the PCM replaces output commands with fixed values in response to certain PCM malfunctions. HLOS mode is used when the system fault(s) is too extreme for the FMEM mode to handle. In HLOS mode, all software operations have stopped and the processor is running on hardware control only. The default strategy for this mode has a minimal calibration strictly to allow the vehicle to operate until it can be serviced. NOTE  In HLOS mode, Self-Test codes will not be output.
Harshness  Any momentary sensation that the driver finds objectionable. See NVH.
HB  Hydro-Boost.
HC  1) Hydrocarbon.; 2) High Compression.
HC    Hydrocarbons
HCA  Hot Cranking Amps  the maximum amount of current a 12V battery can deliver for 10 seconds at 80°F without falling below 7.2V . Compare CCA, CA, RC, Ah.
HCF  Hydraulic Cooling Fan
HCFD  Hydraulic Cooling Fan Drive
HD  1) Heavy Duty; 2) Hot-Dipped galvanized.
HD, H.D. Heavy duty
HDL  Headlamp.
hdtp, HDTP Hardtop
Head  See Cylinder Head.
Header or Header Pipe  An exhaust manifold fabricated from bent tubing (as opposed to being cast), usually tuned to maximize scavenging from the combustion chambers, resulting in more power from the engine. The tubes converge at the collector, which includes a fitting to attach the exhaust system. Some are wrapped or coated to keep heat in so that surrounding components are not damaged. Compare Shorty, Long-Tube Header.
Headlamp (HDL)  A logical input to a module that indicates status of the headlamps.
Heat Exchanger  Any device designed to transfer heat from one fluid to another, including the radiator, intercooler, ATF cooler, PSF cooler, engine oil cooler, heater core, & evaporator core. Contrast Heat Sink.
Heat Gun  An electric torch, or hi-power hair dryer, used mainly for melting plastics & stripping paint.
Heat Riser Tube  A small duct that transfers warm air collected from around the exhaust manifold into the intake system (generally on carburetors before the filter) to aid in fuel vaporization in extreme cold weather.
Heat Sink  Any conductive mass designed to absorb & dissipate heat from other components, such as the finned Aluminum casting used for '92-96 TFI-IV ignition modules. A heat sink is distinct from a heat exchanger in that a sink transfers heat from a solid to a solid, and then slowly radiates the heat (at a lower temperature) to a static fluid.
HEAT VLV INT  Heat Valve Intake (carburetor/vacuum) regulates flow from the exhaust manifold shroud through the heat riser tube to the intake system. AKA Heat Riser Valve
Heated Exhaust Gas Oxygen sensor (HEGO)  An Oxygen Sensor (O2S) that is electrically heated. AKA HO2S.
Heated Oxygen Sensor (HO2S)  An Oxygen Sensor (O2S) that is electrically heated. AKA HEGO.
HEGO  Heated Exhaust Gas Oxygen sensor.
HEGO    Heated Exhaust Gas Oxygen Sensor
HEI    High Energy Ignition
Heim  A popular brand of spherical rod end often used in suspension & steering modification.
Helical Gears  An improved gear design using spiral teeth on circular gears with parallel axes. The advantages include less wear, less noise, more tooth contact, & constant effective radius (smooth output). The disadvantage is an axial load. They are commonly used in transmissions. Contrast Bevel, Herringbone, Hypoid, Spur, Worm.
Herringbone Gears  A rare improvement on the Helical design in which each gear consists of 2 opposite-angle helical-cut tooth sets, which eliminates any axial load. They are sometimes used in transmissions. Contrast Helical, Bevel, Hypoid, Spur, Worm.
Hex or Hexadecimal  a rare numbering system using sixteen possible characters (usually 0-9 and A-F) in each digit. 'Hexadeci-' means sixteen. Nine is '9'; ten is 'A'; twelve is 'C'; fifteen is 'F'; sixteen is '10'; seventeen is '11'; thirty-one is '1F'; thirty-two is '20'.
HFC  1) Hydrofluorocarbon. see Refrigerant; 2) High Fan Control.
HFCF  High Fan Control Fault.
HFP  High Fuel Pump.
Hg    Mercury
HGT    Height
HHDDE  Heavy Heavy Duty Diesel Engine. 
HHDE  Heavy Heavy Duty (gasoline, CNG, or FF) Engine. 
Hi Perf. High Performance
HICV  Hot Idle Control Valve (carburetor/vacuum)
HID  High-Intensity Discharge.
High Fan Control (HFC)  Controlling the high speed cooling fan.
High Fuel Pump (HFP)  An output circuit or signal from the PCM which controls the high speed fuel pump.
High Pinion (HP)  any differential designed for the pinion gear's axis to be above the ring gear's axis. Some require reverse-cut gearsets. The advantage is reduced driveshaft u-joint flex angles; the disadvantage is reduced oiling of the pinion gear & its bearings.
High Steer  any modification of the steering linkage that results in the tie rod assemblies being higher above ground than stock. Most often, it involves re-cutting the tapers in the steering knuckles so the TREs can mount from above.
High Swirl Combustion (HSC)  A cylinder and piston configuration that causes swirling of the air/fuel mixture in the cylinder.
High-Energy Ignition System (HEI)  an ignition system capable of higher-than stock voltage. It is largely a marketing gimmick, with no appreciable performance or reliability improvement over most stock DI systems.
High-Intensity Discharge (HID)  A type of light bulb which uses high voltage to produce visible light in a manner similar to that of neon. They are much more efficient (less heat; lower current) than incandescent bulbs.
Hi-Po  High Performance
Hiss  A steady high noise, like an air leak from a tire. See NVH.
Hitch  A system of mechanisms that joins 2 vehicles (usually a truck & a trailer) for highway towing. The most popular styles are ball, pintle hook/lunette ring, and 5th wheel. There are several types of ball hitch, including tongue and goose-neck. Ball & pintle hitches can be bumper-mounted, or receiver style. Common hitch receivers are built in 4 classes, based on load capacity, with Class III (2" square, 5Kip pulling, 0.5Kip carrying) being the most popular for light trucks. A hitch may also incorporate an anti-sway system &/or a weight-distributing system.
HLA  Hydraulic Lash Adjuster.
HLDT    Headlight
HLOS  Hardware Limited Operating Strategy.
HO  High Output.
HO    High Output
HO2S  Heated Oxygen Sensor.
HO2S    Heated Oxygen Sensor
Hog Head  (slang) see Third Member.
Hook up  1) gain adequate traction; 2) connect with recovery equipment.
Hot Soak  Period of time after an engine operates when its internal heat has not yet dissipated into the environment.
HP  1) HorsePower (usually lower-case); 2) High Pinion; 3) High Performance
HP    High Performance or Horsepower
hp, HP Horsepower
H-Pipe  a method of interconnecting the banks of a dual exhaust system in which a short tube is welded between the 2 main pipes to regulate & tune the pressure waves that cross between the banks. It is the most common factory type of dual exhaust.
HSC  High Swirl Combustion.
HSC    High Swirl Combustion
HSO    High Specific Output
HT    High Tension
HTR    Heater
Hub  The tubular rotating flange containing wheel bearings to which brakes & wheels are mounted. See also Hub Lock.
Hub Lock  A mechanism for connecting a hub to an axleshaft, most often on the front suspension of a 4WD vehicle. They may be operated manually (the most common), pneumatically, electrically, mechanically, or automatically (the 2nd most common). Although some name-brand aftermarket manual hub locks have achieved an elevated status, they are all virtually indistinguishable based on quality, durability, & warranty. The only noticeable difference is in the ease of operation of the selector knob. AKA (slang) Lockout, (slang) Locking Hub, (slang) Hub.
Hum  A low varying noise, like a distant light airplane. See NVH.
Hydraulic  any process, system, or mechanism which operates on the incompressibility of liquids.
Hydraulic Lash Adjuster (HLA)  A mechanism similar to a (solid) lifter which uses engine oil pressure to automatically adjust the valvetrain. AKA Tappet.
Hydraulic'ed or HydroLocked  A condition in which a piston engine has ingested a liquid into the cylinders, causing severe mechanical damage due to the fact that liquids cannot be compressed. It occurs most often when fording deeper than the air inlet duct, but can also occur from fuel flooding.
HydroBoost (HB)  A trademark name for a hydraulic brake booster. Most use fluid & pressure from the power steering pump, but some use a dedicated belt-driven pump & fluid system, or a dedicated electric pump with a pressurized reservoir. Contrast Vacuum Booster.
Hydrogen  A highly flammable gas element. Chemical symbol H.
Hydrogen Cell  an extremely efficient electrical generator with no moving parts, powered by refrigerated (liquefied) Hydrogen & Oxygen, producing only electricity & water. Often used in spacecraft.
Hydrogen Generator  An aftermarket or homemade device usually consisting of a glass jar containing water and a heating element (usually INcorrectly referred to as an electrode) with a hose leading to the intake manifold. Proponents suggest that the bubbles coming off the element are pure Hydrogen, and that the energy it adds to the combustion chamber is greater than that required to generate the electricity consumed by the device, making it economical. There is no scientific basis for this belief, and water cannot be hydrolyzed by a single electrode. Even those few with 2 electrodes that actually hydrolyze water are consuming more electricity than the engine produces as a result of the generator's activity, and are therefore reducing the overall efficiency.
HydroLock  See Hydraulic.
Hypoid Gears  A complex gear system using spiral teeth on non-intersecting non-parallel shafts. They combine the benefits of Helical gears with Bevel, but the teeth abrade each other. They are commonly used in axles. Contrast Bevel, Helical, Herringbone, Spur, Worm.
Hz  Hertz. A measure of frequency in cycles per second.
Hz    Hertz(Cycles Per Second)
i  the standard engineering abbreviation for electrical current, measured in Amperes
I.D. Inside dimension
I.D.    Inside Diameter
IAB  Idle Air Bypass; see IAC.
IAC  Idle Air Control.
IACV    Idle Air Control Valve
IAT  Intake Air Temperature. AKA ACT
IAT    Intake Air Temperature
IATS    Intake Air Temperature Sensor
IC    Integrated Circuit
ICM  Ignition Control Module.
ICM    Ignition Control Module
ICS    Idle Control Solenoid
ID    Identification
IDI  Indirect Injection.
Idle Air Control (IAC)  A pulse-modulated solenoid valve which controls throttle bypass air to help control engine idle RPM. AKA Bypass Air Idle Speed Control solenoid (BPA-ISC).
IDM  Ignition Diagnostic Monitor.
IFI    Indirect Fuel Injection
IFS  1. Independent Front Suspension; 2. Inertia Fuel Shutoff switch.
IGN    Ignition
IGN GND  Ignition Ground.
Ignition  System used to provide high voltage spark for internal combustion engines.
Ignition Control Module (ICM)  The module that controls the ignition system.
Ignition Diagnostic Monitor (IDM)  A signal or circuit from the ignition control module to the EEC/PCM. Compare SPOUT.
II  Integrated Ignition; see EDIS.
Imp Impala
IMRC  Intake Manifold Runner Control.
IMRC  Intake Manifold Runner Control
IMS  Inferred Mileage Sensor. Compare Combo, EMW.
IMS-EUL  Inferred Mileage Sensor/Extended Useful Life Module. See Combo.
IMT  Intake Manifold Tuning.
In.    Inches
in. Hg    Inches of Mercury
Incandescent Bulb  The earliest type of electric light; it operates by passing current through a resistive filament within an inert gas, generating enough heat to maket the filament glow. The inert environment prolongs the life of the filament (usually Tungsten), and certain gases (halogens) accentuate the light produced. They are relatively inefficient & fragile. Compare HID, Fluorescent, LED.
Inch Lbs.    Inch Pounds
Independent Front Suspension (IFS) or Independent Rear Suspension (IRS)  A suspension system which allows either wheel to travel without inducing travel in the opposite wheel. Most incorporate a linkage which partially defeats this function called an anti-sway bar. They have the advantages of lower unsprung weight, better handling, & a smoother ride, but the disadvantages of more complex & delicate construction, more wearing parts, and more expensive alignment. Contrast Solid Axle.
Independent Shop  An auto repair business not associated with a vehicle manufacturer.
Indexing  A procedure for installing spark plugs so that their ground electrodes all point the same direction within the combustion chambers, theoretically to produce smoother, more-reliable power from the engine by causing all chambers to experience precisely the same (and possibly the ideal) propagation of the flame front.
Indirect Injection (IDI)  A diesel cylinder head design in which the fuel injector pintle is recessed in a pocket outside the combustion chamber.
Induction  1) the process of moving air into an engine; 2) an electromagnetic process by which energy is transferred without physical contact. It is the basis for solenoids, motors, transformers, & induction heaters.
Inertia  The physical tendency of a mass (an object) to maintain its current speed & direction (even if stopped) until acted on by an external force. Compare Momentum.
Inertia Switch or Inertia Fuel Shutoff (IFS)  A safety system or device used on vehicles with an electric fuel pump that shuts off the fuel delivery system when activated by predetermined force limits.
Inferred Mileage Sensor/Extended Useful Life Module (IMS-EUL)  Sometimes referred to as 'Infrared Mileage...' due to a typo in the Haynes manual. See Combo.
In-House  Repairs performed at the shop where the owner left the vehicle. Most jobs are this category. Contrast Sublet.
Inj.    Injector
Injection Pressure (IP)  A sensor, signal, or circuit which indicates the pressure in the fuel rail.
Injector  A device for delivering metered pressurized fuel to the intake system or the cylinders. AKA fuel injector.
INT MAN  Intake manifold - the source of vacuum (on gas engines) to all vacuum-operated devices (carburetor/vacuum)
int, Int Interior
Intake Air  Air drawn through a cleaner, regulated by a throttle, and distributed to each cylinder by a manifold for use in combustion.
Intake Air Temperature (IAT)  A sensor, signal, or circuit which indicates the temperature of the intake air. It may be in a runner in the intake manifold, in the air cleaner, or in the duct between them. AKA ACT.
Intake Manifold Runner Control (IMRC)  A system, signal, or circuit which controls airflow through runners in the intake manifold.
Intake Manifold Tuning (IMT)  Control of airflow through runners in a split intake manifold.
Integral  Incorporated by design as a permanent feature of a part. Said of bellhousings, washers, differential carriers. Contrast Captive.
Integrated Electronic Ignition (EI)  An Electronic Ignition system that has the Ignition Control Module (ICM) integrated into the PCM.
Integrated Vehicle Speed Control (IVSC)  Cruise control system incorporated within the PCM, used primarily on diesels & vehicles with electronically-controlled throttle.
Intercooler  A component or system designed to cool the intake air, which has been heated by forced induction. The removal of heat from the pressurized air going into the intercooler increases the air density, which improves combustion efficiency, engine horsepower and torque. On some gasoline engines, the system consists of an additional radiator in the grille, a reservoir (independent from engine cooling system), an electric water pump, a heat exchanger (intercooler) located in the lower intake manifold and tubing to interconnect these components. On most diesel engines, heated & pressurized intake air from the turbocharger outlet is routed to a heat exchanger in the grille forward of the radiator, and then back to the intake manifold(s).
Intermittent  1. A fault that may not be present or identifiable currently; 2. A wiper system or setting that pauses the motor to reduce smearing & noise.
IP  Injection Pressure.
IP    Injector Pump (diesel applications)
IP    Instrument Panel (also see below)
IRS  Independent Rear Suspension.
ISC  Idle Speed Control; see IAC.
ISC    Idle Speed Control
ISO  1) International Standards Organization; 2) Isolate, Isolation.
ISO    International Standards Organization
ITCS    Ignition Timing Control System
ITS    Idle Tracking Switch
IVR  Instrument cluster Voltage Regulator; a calibrated thermostatic switch that regulates power (not voltage) going to an older thermal gauge that still uses a sender designed for 6VDC systems.
IVSC  Integrated Vehicle Speed Control.
IVSV    Idle Vacuum Switching Valve
IVV  Thermactor Idle Vacuum Valve (carburetor/vacuum)
IWE  Integrated Wheel End; a vacuum-operated hub lock & unit bearing system used on some '04-up Ford trucks.
J/B    Junction Block
Jamb Nut  A nut (usually thinner & harder than a standard nut of the same thread size) used to lock a sleeve or an adjacent nut on a threaded shaft by being tightened against it until both nuts bind.
JAS    Jet Air System
J-Nut  A stamped, formed, & hardened sheet metal nut that is J-shaped to slip over an edge. It provides a stronger threading surface for a bolt or screw than the material onto which it is installed. Unlike a U-nut, the male fastener passes through a hole in only one layer of the J-nut.
Jumper Battery  A portable 12V battery with cables & clamps capable of supplying over 120A to a vehicle. Most include an integrated 110VAC charging system and diagnostic charge indicator. Some may include flashlight, air compressor, inverter, radio, etc. AKA Booster Pack.
Jumper Cables  A pair of heavy wires with a connector or clamps capable of supplying over 120A from one vehicle to another for the purpose of instantly starting the engine whose battery is weak, or for slowly charging a dead battery. Longer wires must be of heavier gauge to carry enough current. They may also be used for battery welding. Contrast Booster Cables.
JY  Junkyard.
K Thousand
k/ohms    kilo ohms or Kilohms (1000 ohms)
Kanooter Valve or Kanuter Valve or Kneuter Valve  A joke among mechanics & gearheads to detect amateurs. See KaleCo Automotive.
Keep Alive Memory (KAM)  A volatile portion of the PCM memory where (among other things) adaptive strategies & certain fault codes are stored. KAM must maintain power (KAPWR) even when the vehicle is not operating.
Keep Alive Power (KAPWR)  Dedicated, unswitched power circuit that maintains KAM. Disconnecting the battery for more than ~2min depletes the PCM's built-in backup KAPWR, and causes the KAM to be lost.
Key On Engine Off Self-Test (KOEO)  A test of the EEC system conducted by the PCM with power applied and the engine at rest. Only basic circuit functions are tested; not the logic of the outputs.
Key On Engine Running Self-Test (KOER)  A test of the EEC system conducted by the PCM with the engine running and the vehicle at rest. In addition to all KOEO functionality, KOER also checks the logic of certain signals to certain others. E.g., a high MAF reading with a low RPM will generate a KOER DTC.
Keyless Entry (KE)  A system using a keypad on the driver's door to allow operation of the PL, courtesy lights, & trunk. Contrast Remote Keyless Entry (RKE).
Keystone Clamp  A simple hose clamp comprising a strap loop with a flat-topped arch buckled into it. When the legs of the arch are crimped toward each other, the clamp tightens & the arch becomes a triangle, similar in shape to a keystone.
kg    kilograms (weight)
kg/cm    Kilograms Per Square Centimeter
kHz    Kilohertz
Kip  thousand pounds; Kilo-pounds; x,000lbs.
kit Multiple pieces
Km    Kilometers
km, Km Kilometers
KM/H    Kilometers Per Hour
Knock  1) The sharp metallic sound produced when two pressure fronts collide in the combustion chamber of an engine. It may be caused by hotspots in the combustion chamber (either from poor engine design, carbon buildup, or overheating), high compression, low octane numbered fuel, a lean condition, low oil pressure, valvetrain slack, ignition timing too far advanced (high BTDC), insufficient EGR flow, or incorrect spark plugs. It can cause severe engine damage, including burning through pistons, valve or head damage, overheating, catalyst damage, exhaust leaks, ruptured head gaskets, or backfire (and that resulting damage). AKA Valve Clatter, Dieseling, Preignition, Detonation, Pinging. 2) Any heavy repeating sound, like brick falling on pavement.
Knock Sensor (KS)  A peizolectric sensor installed in the engine block which detects any vibration similar to engine knock. According to some Ford engineers, it causes worse performance than it prevents. If unplugging it causes a code, unscrew it from the block, reconnect it, and tape it to the harness so it can't touch anything metallic.
Knock-Off  1) (slang) a cheap copy; 2) a style of wheel retained on the axle by a single central nut designed to be loosened by striking a wing with a lead hammer, common on antique cars.
KOEC    Key On, Engine Cranking
KOEO  Key On Engine Off.
KOEO    Key On, Engine Off
KOER  Key On Engine Running.
KOER    Key On, Engine Running
KPA  Kilopascal. Metric unit of pressure. 3.386 kPa = 1 inch of mercury (Hg.). 
kPa    kilopascals
KPH  Kilometers Per Hour. Metric unit of speed. 1.6 KPH = 1 MPH; 0.6 MPH = 1 KPH.
KS  Knock Sensor.
KS    Knock Sensor
Ksi  thousand psi; Kilo-pounds per square inch; x,000 psi.
kV    Kilovolt
kW – Kilowatt
L  1) Liters. Metric unit of volume; 2) Left, from the operator's perspective while the vehicle is in motion; 3) Lightning.
L    Liter
L.O.F Lube, oil & filter
L.P.O. Limited Production Order
L/D    Light Duty
L/R Left/Right
L/S or LSD  Limited-Slip Differential.
Ladder Frame  The most common style of frame consisting of 2 parallel members (frame rails, roughly horizontal) running the full length of the vehicle, and connected by perpendicular members (crossmembers). The rails & crossmembers may be channels or tubular (boxed). Contrast Unibody, Monocoque, Subframe.
Lake Pipes  A popular brand of sidepipe, offered as OE on some vehicles like the '67 Corvette L88. 
LB Long bed
LB  1) Light Blue wire or vacuum line; 2) (lb) librae (Latin) = pounds
lb./ft.    Pound Feet
lbf  pounds force, distinguished from lbm (pounds mass).
lb-ft  pound-feet; a measure of torque (typically used for STATIC torque, as in tightening fasteners). 1 lb-ft = 1 lbf at 1 ft from the center of rotation = 2 lbf @ 0.5' = 10 lbf @ 0.1'...
lbm  pounds mass, distinguised from lbf (pounds force).
lbs.    Pounds
LCD  Liquid Crystal Display.
LCD    Liquid Crystal Display
LCM  Lighting Control Module - an electronic component that controls vehicle lighting, inside & out.
LCV  EGR Load Control Valve (carburetor/vacuum)
LD  Light Duty
LD, L.D. Left hand drive
LDDT  Light Duty Diesel Truck.
LDT  Light Duty (gasoline, CNG, or FF) Truck.
LDV  Light Duty (gasoline, CNG, or FF) Vehicle, generally passenger cars and light trucks under 6000 pounds GVWR.
Leakdown Test  a specialized test of a cylinder's ability to hold pressure. Compare Compression Test.
Lean  1) a fuel/air mixture that has more air than is necessary for the fuel to burn. In gasoline engines, it results in slightly more power, but also excessive heat and a tendency to detonate rather than burn. The excess heat also leads to the formation of NOx, oxidation of Aluminum pistons & heads, and overheating. In diesel engines, the engine runs cooler & makes less power. Contrast Rich. 2) a side tilt, as viewed from front or rear.
LED  Light-Emitting Diode
LED    Light Emitting Diode
LED Display  A digital electronic display consisting of an array of LEDs, used to generate characters, symbols, & patterns. Very large displays using several colors of LED can be used to create video displays, such as on blimps. Contrast LCD, VFD.
Left, Left side The driver side of vehicle
LEV  Low Emission Vehicle.
Lf, LF, L.F. Left front
LFC  Low Fan Control.
LFP  Low Fuel Pump.
LG  Light Green wire or vacuum line.
LH Left hand
LHD  Left-Hand Drive.
LHD    Left Hand Drive
LHDE  Light Heavy Duty Engine.
LHF  Left Hand Front, from the operator's perspective while the vehicle is in motion. 
LHR  Left Hand Rear, from the operator's perspective while the vehicle is in motion. 
LHS  Left Hand Side, from the operator's perspective while the vehicle is in motion.
LIFO  Last In First Out. A stock management pattern. Contrast LILO, FIFO, FILO.
Lift  1) Any modification that raises a vehicle's ride height, measured at the top of the arch above each wheel. See  Tire Lift, Suspension Lift, Body Lift; 2) A machine to raise an entire vehicle off the ground for service.
Lifter  An engine part which rides against a cam lobe and operates a pushrod, rocker arm, or valve (directly). Most rotate to reduce wear, and some are hydraulically adjusted. Some have a roller that rides against the cam lobes to reduce friction. AKA Tappet, HLA.
Light Truck  A truck with a nominal cargo capacity less than 2 tons. Contrast Convertible, Coupe, Pickup, Roadster, Sedan, Van, Wagon-body.
Light-Emitting Diode  An electronic device which uses semiconductor material to generate light. They are very efficient (very little heat compared to the light output) and have extremely long lifespans. Contrast Incandescent Bulb. See LED Display.
Lightning  A high-performance option package created by Ford SVO/SVT for F150 XLTs including (among MANY other things) the largest 1/2-ton engine for the given model year & a monochromatic paint scheme either in black, red, or white with "Lightning" logos inside & out. Only one Lightning Bronco was produced for a Ford executive. Compare Custom, XL, XLS, XLT, XLT Sport, Nite, Eddie Bauer.
LILO  Last In Last Out. A stock management pattern. Contrast LIFO, FIFO, FILO.
Limited Slip Posi A rear that allows the opposite wheel to engage if the other begins to spin
Limited-Slip Differential (LSD or L/S)  A type of differential which uses constant friction in an attempt to keep both outputs turning at the same speed, while still allowing true differentiation when necessary. Contrast Open Differential, Locker, Torque-Biasing Differential, Spool.
Lincoln-Locker  An OE open differential which has been welded solid, into a spool. It is named for the popular brand of welding machine. If done incorrectly, the axleshafts can never be removed, OR it can shatter during extreme use.
Liquid Crystal Display (LCD)  A digital electronic display which uses a thin layer of liquid crystal between layers of glass, and behind a polarizing filter. Transparent electrical terminals are embedded in the liquid layer so that, when a voltage is applied, the crystals polarize the light passing through them. The interaction between the crystals & the polarizing filter results in some areas of the display being black while others remain transparent. LCDs do not generate light, but can be placed in front of reflectors or lights to increase contrast. Common applications include pocket calculators, wristwatches, digital wall clocks, & certain computer monitors and TV screens. The effect is that characters or images can be generated in the shapes of the terminals in the display. Contrast LED, LED Display, VFD.
Liquid Wrench  a brand name of penetrating oil.
LLT  Limited LifeTime warranty.
LNG  Liquified Natural Gas. See Natural Gas. Compare CNG; contrast LPG.
Locked  1) equipped with a locking differential (or several); 2) (fasteners) prevented from turning &/or loosening due to vibration or load; contrast Seized.
Locked up  1) (engine) seized; 2) (differential) see Locked.
Locker or Locking Differential or Full-Locker  A mechanism which replaces the standard differential carrier and semi-permanently connects 2 output shafts (as in a differential) using springs & meshed teeth, but no gears. It does not provide true differentiation, but does allow the shafts to rotate at different speeds under certain conditions. The most popular is the Detroit Locker, now owned by Eaton. Contrast Selectable Locker, Mini-Locker, Open Differential, Limited-Slip Differential, Torque-Biasing Differential, Spool.
Locking Hub or Lockout  (slang) See Hub Lock.
Long block An engine that has heads installed. (Also see Short block)
Long Block  An engine assembly consisting of a cylinder block, a crankshaft, all the bearings, all the connecting rods, all the pistons and rings, all the cylinder heads, a camshaft, timing gears/chains/covers, the assembled valvetrain, & most of the seals. Some also include an oil pump, an oil pan, a water pump, an intake manifold, a distributor, & a gasket set. Contrast Short Block, Smallblock, Bigblock.
Long Term Fuel Trim (LONGFT1 and 2)  While the engine is operating in closed loop fuel, the short term fuel trim corrections can be 'learned' by the PCM as long term fuel trim corrections. These corrections are stored in keep alive memory (KAM) in tables that are referenced by engine speed and load (and by bank for engines with two HO2S sensors forward of the catalyst). Learning the corrections in KAM improves both open loop and closed loop air/fuel ratio control. Advantages include  short term fuel trim does not have to generate new corrections each time the engine goes into closed loop; and, long term fuel trim corrections can be used both while in open loop and closed loop modes. Long term fuel trim is represented as a percentage, just like short term fuel trim, however it is not a single parameter. There is a separate long term fuel trim value that is used for each rpm/load point of engine operation. Long term fuel trim corrections may change depending on the operating conditions of the engine (rpm and load), ambient air temperature and fuel quality (% alcohol, oxygenates, etc.). When viewing the LONGFT1/2 PID(s), the values may change a great deal as the engine is operated at different rpm and load points. The LONGFT1/2 PID(s) will display the long term fuel trim correction that is currently being used at that rpm/load point.
Long-Tube Header  A header whose collector is below the oil pan or outside the frame rails. See Header. Compare Shorty.
Low Fan Control (LFC)  Controlling the low speed cooling fan.
Low Fuel Pump (LFP)  An output circuit or signal from the PCM which controls the low speed fuel pump.
LPG  Liquified Petroleum Gas. See Natural Gas.
Lr, LR, L.R. Left rear
LT  Light Truck; a truck in the 1/2- to 2-ton cargo range between 72 & 80" wide with a ladder frame.
LTFT    Long Term Fuel Trim
LUBR  Lifted Uncut early BRonco.
Lunchbox Locker  A simplified type of aftermarket locking differential which only requires replacing the internals; not the entire carrier. They are considered weaker for several reasons. AKA Mini-locker.
Lunette Eye  a heavy-duty hitch system characterized by a large cast-steel ring (the eye) gripped by a pintle hook. It is popular in US military applications, and for tandem heavy truck trailers.
LVW  Loaded Vehicle Weight, defined by Curb Weight + 300 lbs.
LWB    Long Wheel Base
LWR Lower
M  fuel code for Methanol
M/T  Manual Transmission/Transaxle.
M5HD  ZF S5-45 M5OD-HD manual 5-sp OD heavy-duty transmission.
M5OD  A designation for 3 distinct manual transmissions  the Mazda M5OD-R1 used in mid-sized trucks; the Mazda M5OD-R2 (M5OD-LD) used in fullsize light trucks; and 2 similar ZF models the S5-42 (M5OD-LD) & the S5-45 (M5OD-HD, or M5HD) used in fullsize heavy-duty light trucks. All have an Aluminum case with integral bellhousing, and were available in 2- or 4WD configurations. The Mazdas are considered unreliable and are commonly referred to as "Mazdog". The ZF, though not without its own problems, is highly sought-after as an upgrade transmission; particularly the 4WD versions.
M85  Fuel containing 85% methanol alcohol. Fuel methanol (M85) is a mixture of approximately 85% commercial grade methanol (M100) and 15% unleaded gasoline. The resulting fuel has a higher octane rating than unleaded regular gasoline, allowing engine designs with higher compression and corresponding greater engine efficiency and performance (power). Winter blends may contain up to 30% unleaded gasoline to enhance cold engine starts, hence the sometimes-used M85-M70 designation. Severely cold weather may require additional measures for reliable starting. Methanol corrodes some metals and may cause some plastic and rubber components to swell, break down or become brittle and crack, especially when mixed with gasoline. Special materials and procedures have been developed for vehicles and the dispensers used by M85 fuel providers. Since methanol has less energy per gallon, fuel economy in miles per gallon will decrease as the percentage of methanol goes up. However, the FFV uses more of the energy available in the fuel when running on M85-M70 than on gasoline. Flexible fuel vehicles burning fuel methanol have lower exhaust emissions than comparable gasoline vehicles.
mA    Milliamps
MA/MAF    Mass Air Flow
MacPherson Strut  A combined suspension mechanism, incorporating a coilover shock (sometimes as a replaceable cartridge on early versions), an upper pivoting mount, and a rigid lower mount that attaches to a spindle or steering knuckle. It is commonly used on front-wheel-drive & unibody vehicles to save weight & complexity, at the expense of ruggedness and replacement costs. This design eliminates the need for an upper control arm, due to the strut's rigid lower mount controlling the spindle/knuckle in all angles except steering. Contrast Coilover Shock.
MAF  Mass Air Flow.
MAF RTN  Mass Air Flow Return.
MAFS    Mass Air Flow Sensor
MagnaFlux  A process using electromagnetic induction & powdered iron dust to detect flaws in magnetizable parts. The dust particles collect near fractures, making them easier to identify, evaluate, &/or repair.
Malfunction Indicator Lamp (MIL)  A required on-board indicator to alert the driver of an emission related malfunction. May read either 'CHECK ENGINE' or 'SERVICE ENGINE SOON.' Compare CEL, SES.
Mall-Crawler  a vehicle apparently well-equipped for extreme off-roading (or its owner), but meticulously clean & undamaged, indicating total lack of such use. AKA Poser.
MAN VAC  Manifold Vacuum (carburetor/vacuum). Measurement can yield valuable diagnostic information about the engine.
man, Man Manual
Manifold  A device designed to collect or distribute a fluid, like air, exhaust, coolant, or fuel.
Manifold Absolute Pressure (MAP)  A sensor which detects the absolute pressure of the intake manifold air.
Manual Lever Position Switch (MLPS or MLP)  A sensor, signal, or circuit which indicates the selected drive modes of the transmission. AKA NSS, PNP, TR, DTR.
MAP  Manifold Absolute Pressure.
MAP    Manifold Absolute Pressure
Marvel Mystery Oil (MMO)  An aftermarket brand of fluids; particularly, an oil/fuel additive that looks similar to ATF.
Mass Air Flow (MAF)  A system or sensor which provides information on the mass flow rate of the intake air to the EEC/PCM for engine management.
Mass Air Flow Return (MAF RTN)  A return (ground) circuit for the MAF sensor signal.
MAT    Manifold Air Temperature
Match Mounting Tires  A technique used to reduce radial runout and tire spring rate on tire and wheel assemblies. Excessive runout is a source of ride complaints and match mounting can be used to minimize the runout. There are two ways to use match mounting  positioning of the tire on the wheel and positioning the wheel on the hub.
MayPops  (slang) cheap or treadbare tires.
MC  Master Cylinder; the input device for a manual (pedal) hydraulic system. Commonly used in hydraulic brake & clutch systems, sometimes sharing a reservoir. See Slave Cylinder.
MCS    Mixture Control Solenoid
MCT    Manifold Charge Temperature
MCU  Motronic Control Unit. See EEC.
MD  Misfire Detection.
Mechanical Secondary Air Injection  A pump driven system for providing secondary air using a belt driven pump. Contrast Pulse Air Injection System & Electronic Secondary Air Injection.
Mem.    Memory
MEM/CAL    Memory Calibration Chip
Methanol  Wood alcohol; CH3OH. An inexpensive but poisonous fuel additive used to reduce the cost of fuel, and emissions. Blends containing more than ~5% methanol require special engine management & fuel system materials. See M85.
mfd.    Microfarads
MFI  Multiport Fuel Injection.
MFI    Multiport Fuel Injection
MFS  Multi-Function Switch.
MHDDE  Medium Heavy Duty Diesel Engine. 
MHDE  Medium Heavy Duty (gasoline, CNG, or FF) Engine. 
mi, Mi Miles
Microprocessor  A digital processor on a chip which performs logical operations on data.
MIL  Malfunction Indicator Lamp.
MIL    Malfunction Indicator Light
Military Wrap  A method of reinforcing a leaf spring pack by wrapping the 2nd leaf around the eyes on the 1st leaf. If the eye fails, the 2nd wrap secures the pack to the vehicle temporarily.
MilSpec  Military Specifications; a stringent set of design standards for almost any part or material.
Mini-Locker  An aftermarket part which replaces the contents of an open differential carrier with a spring & tooth mechanism to semi-permanently lock the outputs together. Contrast Locker (Full-Locker).
Mini-Spool  An aftermarket part which replaces the contents of an open differential carrier in order to lock the outputs together. Contrast Spool (Full-Spool).
Minivan  A midsize passenger van under 5000lbs GVWR, generally unibody FWD.
Mint  a vehicle that has been returned to its original condition, as it might have appeared on a dealer's lot after being prepped for delivery.
Misfire (Miss)  Any event in the cylinder that causes a sudden change (decrease) in the speed of the crankshaft.
Misfire Detection (MD)  Circuitry designed to detect a misfire by monitoring changes in acceleration of a wheel mounted on the crankshaft through a CKP.
mldg Molding
MLPS or MLP  Manual Lever Position Switch. See also DTR.
mm    Millimeters
Modular  A Ford V engine family introduced in the early 90s in which each head and the block were considered "modules". It includes the 4.6L V8, 5.4L V8, 8.0L V10, 5.0L V8, & 6.2L V8.
Module  A self-contained group of electrical/electronic components, which is designed as a single replaceable unit.
Momentum  the quantity of energy carried by a moving mass, relative to some fixed point. High speed &/or mass results in high momentum.
Monitor Box  An optional EEC system test device which connects in series with the PCM and its harness and permits measurements of PCM inputs and outputs.
Monocoque  A lightweight style of vehicle construction used in early race cars & airplanes consisting of a stressed structural skin, to which all other components are attached. Contrast Unibody, Ladder Frame.
Motor  1. A device which converts electrical energy into rotating mechanical energy; 2. A device which converts vacuum into linear motion (vacuum motor); 3. An engine (slang)
Mount  A mechanical connection that holds a major component to a vehicle's chassis, such as an engine mount (motor mount), transmission mount, or body mount. Most isolate the component's vibrations from the chassis with rubber &/or a viscous fluid (fluid mount), usually silicone grease or oil. Solid mounts are used in high-load appliacations where occupant comfort is less of a concern than absolute reliability, such as engine mounts for flat-track racers.
mouse, Mouse, Mouse motor Small block Chevy engine
MPG  Miles Per Gallon
MPG    Miles Per Gallon
mpg, Mpg, MPG Miles per gallon
MPH  Miles Per Hour
MPH    Miles Per Hour
mph, Mph, MPH Miles per hour
MPI    Multi Point (Fuel) Injection
MPV    Multi Purpose Vehicle
ms    Millisecond
MT, man Manual transmission
Muffler  A resonating chamber used to reduce sound emissions in an airflow, usually engine exhaust.
Muffler Bearing  A joke among mechanics & gearheads to detect amateurs. See KaleCo Automotive.
Multi-Function Switch (MFS)  A switch that combines the functions of turn signal, hazard, beam select, flash-to-pass, wiper & interval, and sometimes cornering lamp control.
Multiplexing  The process of communicating several messages over the same signal path. The increased number of modules on the vehicle dictates a more efficient method of communication. This process allows multiple modules to communicate with each other through the signal path (BUS+/BUS-). Modules communicate with the powertrain control module using Standard Corporate Protocol (SCP) which determines the priority in which the signals are sent. (See SCP.) Multiplexing reduces the weight of the vehicle by reducing electrical wiring.
Multiport Fuel Injection (MFI)  A fuel-delivery system in which cylinders receive fuel by individual injectors that are opened in groups (usually 2 'banks' which do NOT correspond to the cylinder banks of a V engine). Normally fuel is delivered to each cylinder once per two crankshaft revolutions in four cycle engines and once per crankshaft revolution in two cycle engines. Compare Sequential Multiport Fuel Injection; contrast Central Fuel Injection, Throttle-Body Fuel Injection.
Mumford Link  A method of laterally locating an axle, consisting of 2 long bars attached either to the frame or axle at their far ends, and 3 more bars between them with 2 points of attachment. The system allows the axle to roll (sway) or to move straight up & down, but not laterally. Contrast Panhard Bar, Watts Link.
mV    Millivolts
MY  Model Year.
N.m    Newton Meter
N/D Switch  Neutral/Drive Switch; see Neutral Start/Safety Switch.
NA    Not Available
NAAO  North American Automotive Operations.
NATB  Nationa Auto Theft Bureau.
Natural  A color of plastic without dyes or pigments  semi-transparent milky white or light brown.
Natural Gas (NG)  A system capable of using compressed or liquefied natural gas (CNG/LNG) or liquefied petroleum gas (LPG) as vehicle fuel.
Naturally Aspirated (N/A)  An unforced-induction system which allows air to flow into the intake manifold by atmospheric pressure alone. Contrast Forced Induction, Turbocharger, Ram Air, Supercharger.
NBO2    Narrow Band Oxygen Sensor
NC  1) Normally Closed; 2) National Coarse threads
NCP  Non Compliance Penalty.
Nerf Bar  A medium-weight beam below the rocker panel designed to fend-off minor damage when a vehicle drives off-road, and also as a step. Contrast Step Bar; Rock Slider; Exo-Cage.
Neutral Start/Safety Switch (NSS)  A sensor, signal, or circuit which indicates the selected non-drive modes of the transmission. AKA MLP, MLPS, N/D Switch, PNP, TR, DTR.
New, Old Stock (NOS)  a category of part that is not 'new' in the sense that it might be 20 years old, but has never been installed, and is usually in OE packaging.
NF  National Fine threads
NG  Natural Gas.
NGC    New Generation Controller
NGS    New Generation Star
NIB  New, In the Box - a part or kit in the condition one would expect when buying retail.
Nipple  a tubular fluid connector for a hose. Compare Zerk.
Nite  A cosmetic option package above XLT for '89-92 F150s & Broncos including monochromatic black paint, blacked-out chrome, a body tape stripe that fades from blue to purple or pink to blue (depending on year), and matching upholstery. Compare Custom, XL, XLS, XLT, XLT Sport, Lightning, Eddie Bauer.
NO  Normally Open.
No.    Number
Noise  Any sound that the driver finds distracting or objectionable.
NOM, N.O.M. Not Original Motor
NORS, N.O.R.S. New old reconditioned stock
NOS  1) Nitrous Oxide Systems™, a division of Holley - the largest producer of automotive nitrous-oxide systems; 2) a nitrous-oxide system; 3) New, Old Stock; 4) common shield gas for welding 25% Argon 75% CO2.
NOS, N.O.S. New old stock or Nitrous Oxide
Nos.    Numbers
NOx  Oxides of Nitrogen; the main chemicals responsible for acid rain.
NOx    Oxides of Nitrogen
NP 208  A common early chain-driven 4WD (no internal differential) part-time 2-speed transfer case built by New Process Gear with a fixed front yoke output on the L side. The NP 208F variant was built for Ford trucks. It was replaced by the BW 1342 & 1356 beginning around 1986. Eventually all Ford fullsize 4WD light trucks got the 1356, including the F550 PSTD.
NP 435  A common 4-speed manual transmission built by New Process Gear, known for its robustness & durability, even when used in 5-ton trucks. Although no longer in production, it is still in use in many UPS delivery trucks, and is a popular swap for off-road vehicles.
NPT  National Pipe Threads which are tapered near the tip to form a seal.
NSS  Neutral Start/Safety Switch.
NTSB  National Traffic Safety Board. A federal office which oversees many aspects of motor vehicles. 
Nut  A female fastener that typically provides a pre-threaded hole for a screw or bolt. Machine-threaded nuts are generally hex-shaped. See Grade, U-Nut, J-Nut, Press-Nut.
NVG  New Venture Gear; the new name for New Process.
NVH  Noise, Vibration, Harshness. A classification of vehicle concerns.
NVRAM  Non-Volatile Random Access Memory; a type of RAM that doesn't require power to retain its data.
NVRAM    Nonvolatile Random Access Memory
O  1) fuel code for Other; 2) chemical symbol for Oxygen.
O.A.T.  Organic Acid Technology; a type of engine coolant.
O.D. Outside dimension
O.D.    Outside Diameter
O/S    Oversize
O2    Oxygen
O2S    Oxygen Sensor
OASIS  On-line Automotive Service Information System; the Ford data network used by dealership technicians, service advisors, & parts.
OBA  On-Board Air; a compressed air supply system built into a vehicle, usually a compressor driven by the engine belt, usually with a storage tank. It may be a converted A/C compressor, a dedicated air compressor, or a remote electric compressor.
OBD  On Board Diagnostic.
OBD On-board Diagnostics
OBD I On-board Diagnostics 1
OBD II On-board Diagnostics 2
OBD III On-board Diagnostics 3
OBD-I  (slang) A technically meaningless term commonly used for all types/brands/standards of electronic engine management systems before the OBD-II standard.
OBD-II  A national (and now international) standard for automotive engine management, emissions control, and fault reporting systems required in the US since 1996. It allows a single scanner to connect to all makes & models of vehicles for the purpose of monitoring & diagnosing most operating aspects of the engine and associated electronic systems. Some scanners have substantially more capabilities than others, such as real-time monitoring or reprogramming the engine computer.
OBS  Old Body Style
OC  Oxidation Catalytic Convertor.
OC    Oxidation Catalyst
OCBR  Oklahoma Classic Broncos Roundup; the 2nd-largest early Bronco off-road event held annually, usually in September at the SuperLift ORV Park in Hot Springs, AR.
OCIL  Overdrive Cancel Indicator Lamp. AKA TCIL
OCS  Overdrive Cancel Switch. AKA TCS
OCT ADJ  Octane Adjust.
Octane Adjust (OCT ADJ)  A circuit or shorting connector (jumper) that alters engine strategy to compensate for changes in fuel octane rating.
OD    Overdrive
OD, O.D. Overdrive
OE  Original Equipment. Parts installed on a vehicle at the factory. Contrast Direct-Replacement, Aftermarket.
OE    Original Equipment
OEM  Original Equipment Manufacturer. The original producer of factory-installed parts.
OEM    Original Equipment Manufacturer
OEM, O.E.M. Original equipment manufacturer
Offy  (slang) Offenhauser; a brand name of race engine & performance parts.
OHC  Overhead Cam.
OHC    Over Head Camshaft
OHC, O.H.C. Over head cam
Ohm  1) a physicist who identified the fundamental relationship between voltage (V, Volts), resistance (Ω or R, Ohms), and current (i or A, Amperes) as V = R x i ; 2) the standard measure of electrical resistance; (slang) the procedure of testing resistance or continuity ("Ohming").
OHV  Off-Highway Vehicle. AKA Off-Road Vehicle (ORV). 
OHV    Over Head Valve
Oil-to-Air (O2A)  a heat exchanger such as a transmission, power steering, or engine oil cooler.
OMV or DMV  Office/Department of Motor Vehicles. A state office which typically oversees & administers motor vehicle registration, titles, & driver's licenses.
On Board Diagnostic (OBD)  A system that monitors some or all computer input and control signals. Signal(s) outside of the predetermined limits imply a fault in the system or in a related system.
One-of or One-Off  One-of-a-kind; an unusually-modified or fabricated part or system; strange; unconventional; unique. Contrast OE, Direct-Replacement.
Open Circuit  A circuit which does not provide a complete path for current flow (Off, broken circuit). Contrast Closed Circuit.
Open Differential  A differential which divides the input torque (engine) inversely to the amount of resistance on the outputs (traction). Contrast Limited-Slip Differential, Locker, Torque-Biasing Differential, Spool.
Open rear Non posi rear
Open Loop  A mode of PCM operation during which actator outputs are based on programmed information stored in ROM. The PCM always starts in open loop until certain criteria are met, and many outputs are inactive during this mode. Contrast Closed Loop.
Open-Element Air Filter  A popular style of aftermarket air filter that has no box to keep out underhood air. The common misconception is that the factory box somehow restricts airflow, and that removing the box will allow more air into the engine. Under certain conditions, it may; but durning most modes, the fact that warm underhood air is being consumed reduces the engine's power & efficiency. See CAI. 
O-Pipe  A joke among mechanics & gearheads to detect amateurs. See KaleCo Automotive.
Or  Orange wire or vacuum line.
orig, Orig Original
O-Ring  A simple rubber ring used as a seal. Most have a round cross-section, but some are square, rectangular, or diamond. The term may also be applied to simple rubber seals molded into other shapes than "O".
ORP  Off-Road Park.
ORV  Off-Road Vehicle. AKA Off-Highway Vehicle (OHV).
ORVR  On-board Refueling Vapor Recovery. 
OS    Oxygen Sensor
OSS  Output Shaft Speed.
OTA  Oil-To-Air fluid cooler (heat exchanger).
Otto Cycle  The thermodynamic process (named for a German scientist) which takes place in most gasoline engines (reciprocating & Wankel; 2-stroke & 4-stroke). Contrast Diesel, Sterling, fuel cell.
Output Shaft Speed (OSS)  A sensor, signal, or circuit which indicates the rotational speed of the transmission output shaft.
Overhead Cam (OHC)  An engine configuration that uses a single camshaft positioned above the valves.
Overlay Card  A plastic card used with the monitor box to identify EEC signals for each engine. The card also programs the monitor box for auto mode measurements.
OWL  Outlined White Letters; a style of tire sidewall design. See also RWL.
Oxidation Catalytic Convertor (OC)  A catalytic convertor system that reduces levels of HC and CO.
Oxygen Sensor (O2S)  A sensor which detects oxygen (O2) content in the exhaust gases. Compare HEGO, HO2S.
oz.    Ounce
Ozone  A corrosive toxic blue gaseous form of oxygen (O3) formed naturally by electric discharge or high-altitude exposure to ultraviolet radiation. It blocks UV & other radiation from striking the surface of the Earth, but is broken down by many industrial chemicals including older refrigerants.
ozs.    Ounces
P    Park
P.O.P., Protect-O-Plate A metal tag glued onto the warrantly pamphlet that contained car and owner information. Used by the dealer when warranty work was performed.
P/B    Power Bakes
P/C    Printed Circuit
P/D MTR  Park/Decelerate vacuum Motor; AKA Dashpot (carburetor/vacuum)
P/N    Park/Neutral
P/N    Part Number
P/S  Power Steering
PA  Public Address; a loudspeaker system, which (on vehicles) is typically connected to a CB radio or an emergency siren.
PA    Pressure Air
PAG  1) PolyAlkaline Glycol; an oil used in R-134a systems available in 3 viscosities  PAG-46 (all Fords), PAG-100 (most others, including most retrofit kits), & PAG 150. 2) Premier Automotive Group; Ford's collection of high-end subsidiaries including Lincoln, Volvo, Aston Martin, & until recently, Jaguar and Land Rover.
Panel Van  A van with a 1-piece purpose-built body specifically suilted to its intended purpose, such as UPS delivery vans.
Panhard Bar  A simple method of laterally locating an axle, consisting of a pivot on the frame, a parallel pivot on the axle housing (as far from the frame pivot as possible), and a nearly-horizontal bar between them. It allows the axle to roll (sway) or to move vertically, but not laterally. If the whole axle moves, it follows an arc and shifts toward the frame mount, which is the main drawback to a Panhard suspension. Leaf spring suspensions don't require any lateral control since the leaves provide that strength. AKA Track Bar. Contrast Watts Link, Mumford Link.
PAnt  Power Antenna
Parameter Identification (PID)  Identifies an address in the PCM memory which contains vehicle operating information.
Park/Neutral Position (PNP)  1) A sensor, signal, or circuit which indicates the selected non-drive modes of the transmission. AKA MLP, MLPS, NSS, TR, DTR; 2) A semiconductor configuration of positive-negative-positive. Contrast NPN.
Particulate  Small solid matter found in exhaust gases, especially prevalent in diesel engines.
PAS  Power Assisted Steering. See Power Steering.
PAS    Power Assisted Steering
PATS  Passive Anti-Theft System. A factory anti-theft system which disables the fuel injector drivers if the code chip in the ignition key does not match the stored code.
pb, PB Power brakes
PC  Passenger Car. 
PCM  Powertrain Control Module. AKA ECC, EEC, ECM, ECU, MCU, "brain", "computer", "controller".
PCM  Powertrain Control Module
PCS/PC/SOL    Purge Control Solenoid
PCV  Positive Crankcase Ventilation.
PCV    Positive Crankcase Ventilation
PCV Valve  A replaceable gravity- & flow-controlled 1-way metering valve in the PCV system. Because it is exposed to crankcase sludge, it will fail if not replaced regularly. Its failure can result in engine fires, diluted or contaminated engine oil, accelerated wear throughout the engine, poor economy, DTCs, increased emissions, and NVH.
pdl, PDL, P.D.L. Power door locks
PECV    Power Enrichment Control Valve
Pegleg A rear without posi-traction. Only one wheel operates.
Pernickety or Persnickety  excessively precise in the usage & meaning of words (like I'm doing with this list). 
Perspicacious  easily understood; adept at explanation or teaching.
Perspicuous  keenly observant; adept at understanding.
PFI    Port Fuel Injection
pg, PG Powerglide transmission
PGM-FI Programmed Fuel Injection
Phillips Screw  A style of screw head using a specifically-shaped central cross recess (+) designed to be driven by a correspondingly specifically-shaped tool. It is easily confused with Frearson, JIS, PoziDriv, and others. See Screw. Contrast Slotted Screw, Torx.
Photochemical  The action of light on air pollutants which contributes to smog. 
PI  1) Performance-Improved; a ~1996 revision to the head design of the 4.6L modular engine, standardized ~2001; often confused with 2) Police Interceptor (slang) (a badge on certain Crown Victorias with P71 options); 3) Police Interceptor, a 2011 Ford model.
PIA  Positioned In Assembly - a notation for wiring & connectors
Pickup or Pickup Truck  A light truck built on a ladder frame with a cab separate from its walled, but open-top cargo bed. Contrast Box Van, Convertible, Coupe, Panel Van, Roadster, Sedan, Truck, Van, Wagon-body.
PID  Parameter Identification.
PID    Parameter Identification
Pigtail  An electrical connector with preinstalled terminals, each of which has a short wire attached. It is generally used to replace a damaged original connector, but may be used to add new systems.
Ping or Pinging  1) See Knock. 2) Any light repetitive sound, like a marble hitting a tile floor.
Pinion  A small circular gear that drives another gear. Specifically, the axial gear of the hypoid set in an automotive axle.
PIP    Profile ignition pickup
Pitman Arm  A steering mechanism which converts the rotating motion of the steering shaft into the horizontal movement of the tie rods. Contrast Rack & Pinion.
Pk  Pink wire or vacuum line.
PL  Power Door Locks
PM  Power Mirrors
PMGR  Permanent Magnet Gear Reduction starter motor.
PNL Panel
PNP  Park/Neutral Position switch. See DTR.
PNP  Park Neutral Position Switch
PO  Previous Owner
Polarity  A characteristic of a binary physical phenomenon, such as electricity (which can be polarized + or -) or a magnetic field (which can be polarized N or S).
Polarity-Reversing Circuit  An electronic circuit used to drive a motor, which is capable of driving it either direction by means of reversing the polarity supplied to the motor. Examples include Ford power windows, power locks, power antennae, power seats, power mirrors, power adjustable pedals, & sunroofs. GM typically uses double-wound motors, which are heavier, bulkier, & less efficient, but require simpler switches & circuits to control.
Polarized Light  Visible light which has passed through a polarizing filter, as is commonly found on LCD displays & polarized sunglasses. Once polarized, the light cannot pass through a 2nd filter unless the 2nd is aligned with the 1st. Any change in the alignment results in the light being further dimmed. If the 2nd is 90° offset from the 1st, virtually no light passes. Light is also polarized by LCD (which is how the LCD generates the black areas) or by reflection off glass or water (which is why driving & fishing sunglasses are sometimes polarized to eliminate the glare).
Pole Shoe  A ferrous core within the winding of an electric motor which enhances the strength of the magnetic field. Some starter motors have a swinging pole shoe attached to a lever which acts as a solenoid to push the drive into the ring gear.
Polished  A grinding & sanding process inside a manifold or head port to remove roughness from casting, and thereby improve airflow, power, & economy.
Polyurethane  A resilient & durable thermoplastic polymer, often used for automotive bushings. It is noticeably tougher than traditional black vulcanized rubber, and is easily colored for cosmetic style.
Port  An opening, usually in the intake/exhaust manifold gasket surface of the head where the manifold runners join it.
Port Fuel Injection  See Multiport Fuel Injection.
Portal Axle  An axle assembly whose outboard ends incorporate an offset drive mechanism, placing the majority of the axle's bulk ABOVE the centerline between the roadwheels. This creates a 'portal' between the wheels, allowing greater ground clearance. Some agricultural vehicles use portal axles (often with hydraulic drives); the UniMog truck uses solid portal axles; the HMMWV & Hummer (H1) use independent front & rear portal suspensions; MatTracks (TM) create a portal configuration.
Ported or Port-Matched  A grinding process that attempts to precisely match the shapes & contours of the intake & exhaust manifold runners, gasket openings, & head ports to improve airflow, and thereby improve power & economy.
POS  1) Positive; 2) (slang) Piece of $#!+ .
Posi  (slang) Positraction.
Posi, Posi rear, Posi-traction A rear that allows the opposite wheel to turn if the other becomes stuck (limited slip posi) or both to turn all the time (full time posi)
Positive Crankcase Ventilation (PCV)  A system which forcibly draws crankcase emissions back through the engine where they are burned. The PCV valve regulates the amount of ventilating air and blow-by gas to the intake manifold, and prevents backfire from traveling into the crankcase. The PCV valve should be mounted in a vertical position. Sometimes incorporated with the evaporative emissions system.
Positraction  A particular model of LSD used by GM. It is now owned & manufactured by Eaton.
Potentiometer (Pot)  An adjustable resistance component commonly used as a position sensor for rotatable shafts (Example  TP Sensor). AKA Variable Resistor
Power Ground (PWR GND)  The main ground circuit in the EEC system. Distinguished from signal ground (SIG RET) & case ground.
Power Steering  A system which provides additional force to the steering mechanism, reducing the driver's steering effort. It most often incorporates a hydraulic pump powered by the FEAD supplying pressure to a gear box or rack. See also EVO.
Power Steering Pressure (PSP)  A sensor, switch, signal, or circuit which indicates the pressure in the power steering system.
Power Take Off (PTO)  1. A mechanical connection for using engine power for aftermarket equipment such as hydraulic pumps, generators, & agricultural implements. 2. An EEC input signal used to disable On Board Diagnostic Monitors during PTO(1) use.
Powertrain  See Drivetrain.
Powertrain Control Module (PCM)  The module that controls the EEC system. AKA ECC, EEC, ECM, ECU, MCU, PCM, "brain", "computer", "controller". Compare OBD.
PPM  Parts Per Million. A measure used in emissions analysis.
PPM    Parts Per Million
pr, PR Pair
Preignition  See Knock.
Prerunner  a vehicle built to run off-road race courses at high speeds, but that is much cheaper to build, repair, & operate than a full-on racer. Typically, it is a 2WD lifted truck with lightweight safety features and moderate handling improvements used by the race driver to test & learn the course. 
Press-Nut  A stamped, formed, & hardened spring steel nut without threads that slips over a smooth shaft & bites into it to provide retention. It is not designed to be removed intact, but often can be; especially if installed on a shaft whose surface is relatively hard.
Pressure Feedback EGR (PFE)  A sensor, circuit, signal, or system that monitors EGR pressure with a single-port sensor. Contrast DPFEGR, EEGR, EVP.
PRNDL    Park Reverse Neutral Drive Low
PRNDL or 'prindle'  (slang) shift indicator.
Profile Ignition Pickup (PIP)  A sensor, signal, or circuit which provides crankshaft or camshaft position data for ignition synchronization.
Programmable Speedometer/Odometer Module (PSOM)  A module that processes vehicle speed information for use in various electronic systems, displays speed on an analog face, and displays odometer data in a digital LCD. The PSOM can be programmed to accommodate various tire and axle combinations. It is unaffected by gear ratio changes.
PROM  Programmable Read-Only Memory. ROM without program instructions.
PROM    Program Read Only Memory (chip)
Prop Shaft or Propeller Shaft  See Driveshaft.
Protocol  A set of rules for the exchange of information on a network.
PS  1) Power Seats; 2) Power Steering; 3) Power Sunroof
ps, PS Power steering
PSF  Power Steering Fluid; see ATF.
PSI    Pounds Per Square Inch
PSOM  Programmable Speedometer/Odometer Module.
PSP  Power Steering Pressure.
PSP  Power Steering Pressure
PSPS  Power Steering Pressure Switch
PSTD  PowerStroke Turbo Diesel.
PTFE  PolyTetraFluoroEthylene; the chemical name for Teflon®, a lubricating powder which is sometimes embedded in silicone rubber as a non-stick coating or polish, or in plastic tape as a pipe sealant. It may also be added to plastics, oils, & greases.
PTO  Power Take Off.
pts.    Pints
Pu  Purple wire or vacuum line.
Pulse Width (PW)  The length of time an actuator, such as a fuel injector, remains energized, measured in milliseconds or degrees. Compare Duty Cycle.
Pulse Width Modulation (PWM)  A signal pattern characterized by flat peaks of varying duration but constant height separated by an absence of signal (ground) which controls the intensity of an output by varying the signal duty cycle.
Pump  A device used to raise, transfer, or circulate fluids at a relatively constant pressure. Contrast Compressor.
Punch  1) A tool or system for cutting holes in thin material without rotating the cutting surface; 2) (slang) a Drift.
Punched, Punched Out An engines cylinders have been enlarged or bored out. Also see; .030 over, Bored
Purge Flow (PF)  The quantity of fuel vapor burned in the engine.
Push-Start  1) a technique for starting an engine with a failed starting system, by pushing it up to a speed that will allow the transmission to spin the crankshaft. The minimum speed for an automatic is much higher than for a manual transmission; 2) an early style of TFI-IV ignition system that uses a black module. Contrast CCD.
PVC  PolyVinyl Chloride; a common type of plastic. Often confused with PCV.
PW  1) Power Windows; 2) Pulse Width.
pw, PW Power windows
PWM  Pulse Width Modulation.
PWR    Power to Weight Ratio
PWR GND  Power Ground.
pwr, PWR Power
Pwr.    Power
Quarter or Quarter Panel  The body panel behind the doors, distinguished from the Fender or Wing, which is forward of the doors.
Quick Test  A functional diagnostic test of the EEC system consisting of vehicle preparation and hookup, KOEO, KOER and Continuous Memory Self-Tests.
R  1) combustion code for Otto Cycle Rotary (Wankel) engines; 2) Red wire or vacuum line; 3) Rear, from the operator's perspective while the vehicle is in motion; 4) Resistance (see Ohm).
R&I  Remove & Install - take a part/component out/off & then put it back in/on without repair. For example  when tires are simply rotated, that's R&I 4 wheels. Even if the part/component is being rebuilt, that's a separate job, so the R&I still applies.
R&R Remove and replace or remove and reinstall
R&R  Remove & Replace - take a part/component out/off & put another in/on. For example  an oil change is an R&R of the oil & filter.
R&R    Remove and Replace
R.P.O. Regular Production Order
r.r, R.R. Right rear
R.W.D. Rear wheel drive
R.W.L. Raised white letters
R/A    Resume or Accelerate
R/T    Road/Track
RABS  Rear Antilock Brake System.
RAC    Remote Accessory Controller
Rack & Pinion  1) A common gear system using a straight row of gear teeth (the "rack") and a circular gear in mesh (the "pinion") to convert the rotating motion of the pinion shaft into the linear motion of the rack; 2) A steering linkage using such a gearset. Contrast Pitman Arm.
Radiator  The engine's liquid-to-air heat exchanger(s).
Rag Joint  A type of u-joint consisting of 2 yokes attached to a fiber-reinforced rubber disk, used in steering and driveshafts. AKA Jured Coupling.
Ram  A linear hydraulic actuator.
RAM  Random Access Memory. Memory into which information can be written as well as read. It is typically volatile (does not survive power loss) and much faster than (nonvolatile) EEPROM.
RAM    Random Access Memory
RAM    Remote Anti-theft Modukle
RAM    Ride Air Module
Ram Air  A forced-induction system which uses the vehicle's forward motion to create pressure in the intake manifold. Contrast Turbocharger, Supercharger, Naturally Aspirated.
RAP  1) Remote Anti-Theft Personality module; 2) Retained Accessory Power.
Rap  to strike sharply to induce vibration, as when loosening or removing a stuck part.
RAP    Retained Access Power
rat, Rat, Rat motor Big block Chevy engine
Ratchet  1) a toothed mechanism that allows rotation in only one direction; 2) a wrench incorporating such a mechanism, typically with a square drive for sockets & other tools.
Rattle  A quick irregular but continuous noise, like an ice-cream churn.
RAV    Remote Activation Verification
RBC    Rotary Blade Coupling
RC  Reserve Capacity  the number of minutes a fully charged battery at 80°F can supply 25A without dropping below 10.5V. This indicates the actual amount of enenrgy stored in the battery. Longer time (or higher current) is better, and comes from larger, heavier batteries. Compare CA, CCA, HCA, Ah.
RCC    Rear Climate Control
RCC    Remote Climate Control
RCM    Restraint Control Module
RD, R.D. Right hand drive
RDM    Rear Door Module
RDS    Radio Display System
REC    Receive
RECAL    Recalibrate
Recall  A program authorized by the manufacturer whereby a known fault or issue with a motor vehicle is repaired, usually without additional cost to the owner, & usually without expiration. A recall generally applies to a very specific group of vehicles, and the manufacturer identifies each VIN to the OMV of each state, which then furnishes the manfuacturer with the registered owner's name & mailing address. Recalls are generally overseen by NTSB &/or DOT, but are administered by the manufacturer. AKA FSA. Contrast TSB.
RECIRC    Recirculation
Red Wrench  (slang) a torch, usually acetylene due to its reddish flame. See also Blue Wrench.
REDOX  Reduction/Oxidation Catalytic Convertor.
Reduction/Oxidation Catalytic Convertor (REDOX)  An advanced catalytic convertor system. At low temperatures, it reduces levels of HC and CO. At high temperatures, it also reduces levels of NOx.
Reefer  (slang) a refrigerated semi-trailer.
Reference Voltage (VREF)  A dedicated circuit that provides a 5.0 volt signal used as a reference by certain sensors.
Refrigerant  The working fluid in heat transfer systems that operate below ambient temperature. The most common refrigerant for mobile A/C is R-134a (Suva®DuPont), a non-chlorinated hydrofluorocarbon (HFC); older systems used R-12 (Freon®DuPont), a chlorinated fluorocarbon (CFC) known to have several adverse environmental effects. Contrast Coolant.
Refurbished  a part or system that has been brought back into nominal working condition, though not necessarily by the original manufacturer, or to original specifications.
Regenerative Brakes  A system for slowing a moving vehicle which stores the energy, instead of simply converting it to heat as normal brakes do. Regenerative braking systems may use dynamos to store the energy electrically, air compressors or hydraulic pumps to store it as pressure, or other means. They are most commonly used on commercial & industrial vehicles which make frequent stops, like city buses.
Relay  A generally electromechanical device in which a high-current (load) circuit is opened or closed by changes in a low-current (trigger) circuit. A common relay is an electromagnetically-operated switch, in which a small current passing through an electromagnetic coil pulls or pushes a steel slug or plate connected to a switch. Some act through a sealed glass bulb which may contain Mercury contacts. Other relays are solid-state & work similarly to transistors, but transistors' output is proportional to the input, and relays are on-off. Almost all Ford vehicles use a starter relay, and most are mounted to the right inner fender or wheelwell near the battery. Often confused with Solenoid.
Relay Module (RM)  A module containing two or more relays.
REM  Rear Electronic Module.
REMAN Remanufactured
Remanufactured  a part or system that has been professionally returned to original working specifications, usually by the original manufacturer.
Remote Anti-Theft Personality (RAP) Module  a module combining functions of earlier remote keyless entry, theft, and illuminated entry modules. Compare GEM. Contrast Retained Accessory Power.
Repetitive Spark  Multiple firings of individual spark plugs at engine speeds below 1000 RPM to improve idle quality and improve emissions. AKA Multiple Spark Discharge (MSD) (TM).
repro, Repro Reproduction
REQ, REQD Required
rest, resto, Resto Restoration
Restified  (slang) a vehicle that has been returned to working condition using much more modern parts & systems than it originally had, such as EFI in a 1960's vehicle.
Restored  a vehicle that has been returned to its original condition, as it might have appeared a short time after being purchased.
Retained Accessory Power (RAP)  An optional feature that allows certain key-switched electrical systems to continue working with the key off for a limited time. Most cancel when a door is opened. Compare Battery Saver. Contrast Remote Anti-Theft Personality module.
Return (RTN)  A dedicated sensor ground circuit.
RF  Radio Frequency. A band of electromagnet frequencies between ultrasonic & microwave.
RF    Radio Frequency
RF    Right Front
Rf, RF, R.F. Right front
RFA    Remote Function Actuator
RFF    Roller Finger Followers
RFI  Radio Frequency Interference. A high-frequency form of EMI.
RFI    Radio Frequency Interference
RFID    Radio Frequency Identification
RFWS    Right Front Wheel Speed
RH Right hand
RH    Right Hand
RHD  Right-Hand Drive.
RHF  Right Hand Front, from the operator's perspective while the vehicle is in motion.
RHR  Right Hand Rear, from the operator's perspective while the vehicle is in motion.
RHS  Right Hand Side, from the operator's perspective while the vehicle is in motion.
Rich  a fuel mixture that contains insufficient air for the fuel to burn completely. In gasoline engines, it results in a cool-running engine, soot both in the exhaust stream and as deposits in the combustion chambers, HC emissions, CO emissions, reduced power, blow-by, oil thinning by fuel contamination, catalyst overheating, and reduced fuel economy. In diesel engines, the engine runs hot & makes more power. Contrast Lean.
Right, Right side The passenger side of vehicle
RIM    Radio Interface Module
RIM    Rear Integration Module
RITS  Run In The Sun; an off-road event for Bronco owners & their friends held each year in the SouthEast, usually organized by the webmaster of FourDoorBronco.
RKE  Remote Keyless Entry - a system for operating the PL, trunk, &/or alarm via a radio-transmitter key fob. Some also allow remote starting. Contrast Keyless Entry (KE).
RKE    Remote Keyless Entry
Rly    Relay
RM  Relay Module.
RM    Relay Module
Roadster  An open passenger car with 2 doors, with or without a removeable/collapsible roof. Contrast Convertible, Coupe, Pickup, Sedan, Truck, Van, Wagon-body.
Roar  A low steady continuous noise, like inside a cruising jet airliner.
Rock Rash  (slang) Body damage due to contact with terrain while wheeling. AKA Environmental Streamlining.
Rock Slider  A heavy beam below the rocker panel designed to carry the weight of the body over rocks when a vehicle drives off-road. Contrast Step Bar; Nerf Bar; Exo-Cage.
Rocker or Rocker Arm  A lever in the head operated by the camshaft (possibly through lifters & pushrods) which opens the valve. Some have a roller to reduce friction.
Rocker Panel  The body panel below the doors.
Roller (Lifter or Rocker)  A low-friction design of valvetrain using a wheel between the lifter & cam lobe, &/or between the rocker & valve.
ROM    Read Only Memory
RON  Research Octane Number. The laboratory-measured octane number of an automotive fuel. Contrast actual octane number, nominal octane number.
Root-Mean Square (RMS)  A mathematical operation to produce a useable value for signals whose average value is 0. Necessary for all AC signals, and generally calculated based on 60Hz. DMMs which specify 'RMS' on their packaging calculate it based on the actual measured frequency, and are therefore far more accurate for most automotive signals, whose frequencies often vary.
Rotary  See Wankel.
Rotor  the insulated conductor within a distributor.
Routine  A group of related tasks, such as a series of diagnostic tests.
RPM  Engine Revolutions Per Minute.
RPM    Revolutions Per Minute
RPO    Regular Production Option
RR    Right Rear
rr, RR Rear
RS Rally sport
RSA    Rear Seat Audio
RSC    Roll Stability Control
RSS    Road Sensing Suspension
RT    Right
RTD    Real Time Dampening
RTN  Return. AKA Ground.
RTN    Return
RTV  Room-Temperature Vulcanizing - a rubber that cures & crosslinks without additional heat, such as silicone rubber sealants.
Rumble  A low heavy continuous sound accompanied by a vibration, like a skateboard on rough pavement.
Run-on  A symptom experienced by carburetor engines in which the throttle plate(s) remain partially open after key-off, allowing enough air to continue to draw fuel into the dirty or overheated combustion chambers. The hot deposits or metal ignite the fuel mix without a spark, causing the engine to continue running, albeit roughly, & at a VERY low speed. This symptom is often confused with preignition. EFIs don't suffer from this because the injectors shut down at key-off.
RV  1) Recreational Vehicle; 2) Rear-View mirror.
RV    Recreational Vehicle
RWAL    Rear Wheel Anti Lock
RWC Rear wheel cylinder
RWD  Rear Wheel Drive. A powertrain system which delivers engine power to a differential in the rear axle only. Contrast FWD, AWD, 4WD. 
RWD    Rear Wheel Drive
RWL  Raised White Letters; a style of tire sidewall design. See also OWL.
RWS    Rear Wheel Steer
S  1) Spark port (carburetor/vacuum) A nipple on a carburetor whose vacuum response is designed to control the vacuum advance of a distributor; 2) Stator terminal on an alternator or voltage regulator, ~1/2 B voltage when the alternator is working properly; 3) combustion code for Otto 4-Stroke-Cycle Piston engines.
SAE  Society of Automotive Engineers, now SAE International.
Safety Certification Label  A sticker showing the manufacturer, build date, VIN, & other information needed to show compliance with vehicle safety laws & standards. It is most often applied in the driver's door jamb area, and usually contains a bar code version of the VIN. Some also indicate installed options & cargo capacities. AKA VIN Sticker, Door Jamb Sticker.
Saloon  See Sedan.
SAS  Solid Axle Swap
SB Small block or short bed
SBC    Single Bed Converter
SBC, sbc Small block Chevy engine
SBD    Strategy Base Diagnostics
SC  Supercharger or supercharged.
SC    Supercharged
Scan Tool (ST)  A device that interfaces with the PCM and communicates information on a data link. Most can read codes and display them either as a flashing light, or as text. Some can read live data from the PCM. Very expensive models (usually factory-licensed) can retrieve &/or edit EEPROM data within the PCM and other modules.
SCDS  Speed Control Deactivator Switch; the secondary (failsafe) cruise control cancel switch. An early type is the subject of a massive recall due to fires.
SCP  Standard Corporate Protocol.
Screw  1) A typically light-duty fastener, generally with a recessed-drive head for wrist-operated tools, and often to be used in unthreaded holes. See Slotted, Phillips, Torx. Contrast Bolt. 2) (slang) An F150 SuperCrew (4-door short bed).
sdn, sed, Sdn, Sed Sedan
Seat Cover  (slang) an attractive female passenger.
Secondary Air  Air provided to the exhaust system anywhere downstream of the exhaust valves.
Secondary Air Injection (AIR)  A pump-driven system for providing secondary air.
Secondary Air Injection Bypass (AIRB)  See TAB.
Secondary Air Injection Diverter (AIRD)  See TAD.
Sedan  A passenger car with 4 doors. Contrast Convertible, Coupe, Pickup, Roadster, Truck, Van, Wagon-body.
SEFI    Sequential Electronic Fuel Injection
Seized  permanently un-turnable due to metal corrosion, deformation, or failure; contrast Locked (2).
Selectable Locker or Selectable-Locking Differential  An aftermarket differential with a mechanism that can convert it to behave as a spool when the operator chooses. Contrast Open Differential, Limited-Slip Differential, Locker, Mini-Locker, Torque-Biasing Differential, Spool, Mini-Spool.
Self-Clearancing  (slang) allowing moving parts (such as oversized tires) to wear against other parts (such as wheelwells & fenders) until there is no more interference.
Self-Test  A general term for three distinct aspects of the EEC system Quick Test  Key On Engine Off, Key On Engine Running, and Continuous Memory. Compare OBD.
SEMA  Specialty Equipment Market Association. A trade guild of businesses who supply non-OE vehicle parts, OR a trade show they host each year. Member businesses cooperate closely with automakers to develop high-quality aftermarket parts.
Semi-Floating Axle  An axle assembly whose axleshafts bear the weight of the vehicle only at their outboard ends. Their inboard ends 'float' in the differential side gear splines. Contrast Full-Floating Axle.
Semi-Truck  A truck built in 2 or more independent interchangeable sections  usually, a tractor containing the drivetrain, cab, & hitch; and a trailer for cargo or equipment.
Sensor  The generic name for a device that senses either the absolute value or a change in a physical quantity such as temperature, pressure or flow rate, and converts that change into an electrical quantity signal. A sensor is typically an analog device. Its digital counterpart is a switch.
Sensor Ring  See Tone Ring.
Sequential Multiport Fuel Injection (SFI)  A multiport fuel delivery system in which each injector is individually energized and timed relative to its cylinder intake event. Compare Multiport Fuel Injection.
Servo  A remote actuator which can be regulated to a precise position, as opposed to simply an extreme of its range of motion. Common examples include cruise control servos, HVAC door servos, & power seat or power mirror motors WITH memory. Those without memory capability are simply motor-driven mechanisms, but do not qualify as servos.
SES  Service Engine Soon light. See MIL.
SES    Service Engine Soon
SET A complete set
SFA  Solid Front Axle. See Solid Axle
SFI  Sequential Multiport Fuel Injection.
SFI    Sequential Fuel Injection
SFR  Single-Function Reservoir.
Shackle Flip  a method of lifting a vehicle originally built with the shackle & bracket below the leaf spring.
Shield  A conducting sleeve that surrounds wires to isolate them from electromagnetic interference (EMI).
Shift Indicator Lamp (SIL)  A lamp that indicates the preferred shift points for manual transmission/transaxle vehicles.
Shift Solenoid (SS)  A device that controls shifting in an automatic transmission.
Shipping weight The weight of the vehicle with regular equipment and with grease and oil where required. This does not include the weight of gasoline and antifreeze.
SHO  Super High Output.
Shock  1) the sensation of electricity passing through one's body; 2) a physical jolt, or sudden dramatic temperature change (thermal shock); 3) (slang) a shock absorber.
Shock Absorber  The misnomer for a spring damper, typically gas-charged oil-dampened. The spring & suspension mechanism actually absorb the shock; the "shock absorber" merely slows the suspension & the spring's reaction to keep the tires in contact with the surface better.
Short block An engine that does not have heads installed. (Also see Long block)
Short Block  An engine assembly consisting of a cylinder block, a crankshaft, all the bearings, all the connecting rods, all the pistons and rings, & few if any seals. Some also include a camshaft, timing gears/chains/covers an oil pump, an oil pan, & a gasket set. A short block does NOT include cylinder heads, valve covers, or intake manifold. Contrast Long Block, Crate Engine, Smallblock, Bigblock.
Short Circuit  A connection between a circuit and any other point. While generally used to indicate an undesirable connection, all wires are short circuits between the terminals they connect. The expression 'short' indicates that there is very little resistance between the 2 points. The most common type is a short from power to ground, which results in extremely high current flow, causing fuses to burn, wires to melt, or fires to start. Contrast Open Circuit, high resistance, Off.
Short Term Fuel Trim (SHRTFT1 and 2)  If the oxygen sensors are warmed up and the PCM determines that the engine can operate near stoichiometric air/fuel ratio (14.7 to 1 for gasoline), the PCM goes into closed loop fuel control mode. Since a common oxygen sensor can only indicate rich or lean, the fuel control strategy must constantly adjust the desired air/fuel ratio rich and lean to get the oxygen sensor to 'switch' around the stoichiometric point. If the time between switches are the same, then the system is actually operating at stoichiometry. The desired air/fuel control parameter is called short term fuel trim where stoichiometry is represented by 0%. Richer (more fuel) is represented by a positive number and leaner (less fuel) is represented by a negative number. Normal operating range for short term fuel trim is +/- 25%. Some calibrations will have time between switches and short term fuel trim excursions that are not equal. These unequal excursions are used to run the system slightly lean or rich of stoichiometry. This practice is referred to as using 'bias'. For example, the fuel system can be biased slightly rich during closed loop fuel to help reduce NOx. Values for SHRTFT1 and 2 may change a great deal on a scan tool when the engine is operated at different rpm and load points. This is because SHRTFT1 and 2 will react to fuel delivery variability that can change as a function of engine rpm and load. Short term fuel trim values are not retained after the engine is turned off.
Shorty or Shortie or Short-Tube Header  A header whose collector is above the oil pan and inside the frame rails. See Header. Compare Long-Tube Header.
SI  1) Sequential Injection; 2) System International d'Unites (the modern international version of the metric system).
Side Gapping  A modification of a standard spark plug so that the ground electrode approaches the side of the center electrode, instead of covering the end. The concept is that the spark will then propagate the flame front more rapidly & evenly through the combustion chamber, increasing power & economy. But the spark is concentrated to smaller areas on both electrodes, so it erodes both more rapidly, and is more susceptible to fouling. Its benefits are also questionable.
Sidepipe  An exhaust tailpipe that runs along the side of the body under the door & exits forward of the rear tire. They are more common on grand touring coupes or roadsters, but are also popular for off-road trucks. A well-known brand was Lake, which was offered as OE on some Corvettes.
SIG RTN  Signal Return.
Signal  A fluctuating electric quantity, such as voltage or current, whose variations represent information.
Signal Return (SIG RTN)  A dedicated sensor ground circuit that is common to two or more sensors.
SIL  Shift Indicator Lamp.
Silicon  A black nonmetallic element; the most common in the Earth's crust, as a compound with Oxygen (Silicon Dioxide=Sand=Glass). It is used in semiconductors and in steel alloys, among many other applications.
Silicone  A durable colorless polymer used in brake fluid, grease, and (for a short time) in prosthetics - particularly breast implants. Silicone grease does not dissolve in water or gasoline, and so is often used in vehicles, but it can block fuel injectors. Its grease can be formulated with a high dielectric, and is often referred to as "dielectric grease". Another forumlation ("electrical grease") is thinner and doesn't interfere with electrical contacts.
Silver cadmium A type of plating used on some automotive parts such as brake master cylinder lids, electrical relays, etc. Similar to gold cadmium only it has a silver color.
Single-Function Reservoir (SFR)  A fuel reservoir used on '84-89 single-tank Ford trucks which may contain a filter.
Sipe  1) the small veins in the tread of a tire, designed to allow water to flow away from the larger tread blocks; 2) to modify the tread surface of a tire to improve its performance in specific terrain.
SIPS    Side Impact Protection System
SIR    Supplemental Inflatable Restraint
Six pack No, not that! Three two barrel carburetors
SJB  Smart Junction Box.
Skinny Pedal  (slang) accelerator; a reference to using engine power rather than skill or good sense.
Slave Cylinder  The output device for a manual (pedal) hydraulic system. The term applies to drum brake wheel cylinders, hydraulic calipers, & clutch slave cylinders. See Master Cylinder.
Sleeper A high performance car that has the appearance of being average. (Ex. A 4 door wagon with a 409 engine)
Slider  1) A sliding window; 2) A rock slider.
Slip Yoke  A telescoping connection between a splined shaft (usually the output shaft of a transmission or transfer case) and a U-joint in a driveshaft. Most fullsize Ford trucks use a slip yoke at the forward end of the rear driveshaft, except those with the BW 1342 t-case.
Slip Yoke Elimination (SYE)  a popular modification to a transfer case from slip-yoke to fixed-yoke. It prevents a short driveshaft on a long-travel suspension from falling out of the t-case.
Slotted Rotor  A disk brake rotor which has had spiral slots machined into its surface. Historically, this was done to improve braking performance due to poor friction materials which contained adhesives & other contaminants that produce gas when heated (causing the pads to 'float' away from the rotor like a hovercraft), and which also produce varnish on the friction surfaces. The slots not only allow this gas to escape, but also clean the pads. Modern pads do not suffer from these problems, so modern slots are purely cosmetic. However, removing metal from the disk's surface causes the pads & rotors to wear faster, and causes heat to build up to higher temperatures; both of which reduce braking effectiveness. See Cross-drilled Rotor, Wilwood FAQ.
Slotted Screw  A style of screw head using a simple, straight, central groove designed to be driven by a correspondingly simple, straight-edged tool. AKA Flathead. See Screw. Contrast Phillips, Torx.
Slushbox  (slang) An automatic transmission. Contrast Grindbox.
Smallblock  An engine family of varying displacements that share some parts & characteristics, most of which have lower displacement than most of those in another family of engines from the same manufacturer. Contrast Short Block, Long Block, Bigblock.
Smart Junction Box  A fuse panel which includes certain functions of the GEM, LCM, DDM, or RAP.
SME  Society of Manufacturing Engineers.
Smog  1) Smoke & fog; 2) (slang) vehicle emissions
Smog Pump  (slang) Secondary Air pump
Smogged  (slang) Tested for emissions
Smoke Test  1) The common method to find a leak in the evaporative system, using a special machine that generates visible (but non-toxic/nonflammable) smoke; 2) (slang) applying power to a circuit with a known but hidden fault, causing the fault to get hot enough to put off smoke, or at least become more apparent in some way, usually resulting in more damage.
Snap Ring  A hardened spring steel ring with a gap and an eye on each end for a tool to grip & stretch the ring for installation/removal. Internal snap rings have eyes inside, and fit into an interior groove; externals have the eyes outside, and fit into an external groove.
Snatch  A recovery technique that uses the momentum of the fast-moving extraction vehicle to overcome the inertia and other forces acting on the stuck vehicle. It is typically the most-dangerous & most-destructive technique.
Snatch Strap  An elastic recovery strap which reduces the impact on the vehicles and converts momentum to force more smoothly (and more safely).
Sniffer  (slang) An electronic device used to detect chemicals by sampling air; most often, refrigerant or exhaust gas.
SOA  Spring-over axle; a method of lifting a vehicle originally built with the leaf springs passing under the axle tube. Applies mainly to Jeep & Dodge.
SODD  Special Order Design Division
SOHC    Single Overhead Cam
Sol V  Solenoid valve; a valve (usually to control vacuum) operated by an integral solenoid, such as the TAB, TAD, EVR, CANP, IAC, & fuel injectors.
SOL/Sol.    Solenoid
Solenoid  A device consisting of an electrical coil which, when energized, produces a magnetic field in a plunger which is pulled to a central position. A solenoid may be used as an actuator in a valve or switch. A solenoid-operated switch is called relay. Few Fords before 1990 used a starter with a solenoid, but even after that, a starter relay was often still used. Most other brands of '75-95 US vehicles use only a starter solenoid with no relay, which results in most parts suppliers calling Ford-type relays 'solenoids'.
Solid Axle  A suspension unit (typically a driving axle) which rigidly connects the 2 wheels, most often by a tube containing a differential and axleshafts. Front (steering) solid axles also include steering knuckles & universal joints of some type. Contrast IFS/IRS.
Solid Axle Swap (SAS)  The process of retrofitting a solid axle to a vehicle originally built with an independent axle; most commonly, the front.
Spanner  A style of wrench that grips the face of the fastener (usually a large, thin nut), as opposed to the sides. Common applications include antenna nuts & wheel bearing adjusting nuts on 4WD vehicles.
Spark Output (SPOUT)  A shorting plug, connector, signal, or circuit which transmits the desired spark timing information from the PCM to the ICM.
Spark Plug  A gasoline engine part designed to withstand high temperature & voltage (using a ceramic insulator) and produce a spark inside the combustion chamber to ignite the fuel/air mixture. See Gap, Indexing, Side Gapping.
Speed  The magnitude of velocity (regardless of direction); distance divided by time.
Speed Shift  Shifting a manual transmission without using the clutch by working the throttle to match the engine speed to the transmission. Commonly used in drag racing & heavy trucks, but also when the clutch system has failed in some way. Contrast Double Clutch.
SPFI    Sequential Port Fuel Injection
Spider Gears  (slang) The smallest gears within a normal open differential on the pinion shaft, technically called pinion gears. They mesh with the side gears and are responsible for thedifferential action.
SPK    Spark Control
Spool or Full Spool  A single solid piece of metal which connects an axle's ring gear to the axleshafts, providing no differentiation. Contrast Differential, Locker. Compare Lincoln-Locker.
SPOUT  Spark Output.
SPOUT    Spark Output
spt cpe, Spt Cpe Sport coupe
spt sed, Spt Sed Sport sedan
Spur Gear  A common & inexpensive gear design using straight teeth on the gear's circumference, and parallel shafts. It produces wear, noise, & irregular output speed. Contrast Helical, Bevel, Herringbone, Hypoid, Worm.
Squeak  A high brief noise, like new tennis shoes on a clean floor.
Squeal  A high continuous noise, like a slipping drivebelt.
SRE  Spherical Rod End; a swivelling connection used mainly in steering & suspension systems. It contains no rubber, and so produces much more precise movement, at the expense of transmitting more NVH. See Heim.
SRI    Service Reminder Indicator
SRS    Secondary Restraint System
SRS    Supplemental Restraint System
SS Supersport
SS  1) Shift Solenoid; 2) Super Sport; a high-performance vehicle, usually a V8 coupe (muscle car).
SSI    Solid State Ignition
ST  Scan Tool.
STA  See "S" (definition 2).
Stake  A procedure to prevent a metal part from sliding, turning, or moving by bending a small section of it so that it interferes with other parts.
Standard Corporate Protocol  A communication language used by most automotive manufacturers for exchanging bi-directional messages (signals) between stand-alone modules and devices. Two or more signals (multiplexed) can be sent over one circuit. Included in these messages is diagnostic data that is output over the BUS+ and BUS - lines to the data link connector (DLC). This information is accessible with a scan tool.
Standing Wave Ratio (SWR)  A measure of the efficiency of a radio transmitter (usually a CB) & its antenna system. The ideal value is 1, meaning all of the energy leaving the radio's output is radiated from the antenna. Deviations from this can be caused by poor connections, coiled antenna cables, or improperly tuned antennae (wrong effective length for the average frequency). It is not related to Ground Plane, although both affect transmitting range. SWR does not affect reception.
STAR    Self
Static  Unmoving/stagnant/still. Contrast Dynamic.
std, Std, S.A.E. Standard
Step Bar  A lightweight beam below the rocker panel designed to carry the weight of a few people as they enter/exit the vehicle. Contrast Rock Slider; Nerf Bar; Exo-Cage.
Sterling  A medium truck manufacturer owned by Ford.
Sterling Cycle  A thermodynamic cycle used for low-torque low-maintenance applications, such as remote agricutural water pumps. The cycle is among the most efficient yet known, and can operate on virtually any fuel that creates heat. It was experimentally adapted for vehicle use in postal vans in the early 90s.
STFT    Short Term Fuel Trim
STO    Self Test Output
Straight Pipe  An exhaust system with no muffler.
Stroked An engine that's had the length of it's piston stroke increased
Strut  Any rigid structural member, usually within the suspension system. See also MacPherson Strut.
Stupid Tax  (slang) the cost of vehicle repairs, usually those due to exuberant or reckless driving.
Subframe  a removeable frame substantially heavier than the rest of the vehicle structure, but substantially smaller than the complete vehicle. It is commonly used to support the engine & front suspension in FWD monocoque & unibody vehicles, and sometimes for the rear suspension. Contrast Ladder Frame.
Sublet  Repairs performed at a different shop than the one the owner left the vehicle in, such as a transmission rebuilder or a painter. Generally, the vehicle owner isn't aware of sublet jobs because the primary shop handles the transportation & warranty, and integrates the cost into its own bill. Contrast In-House.
SULEV  Super Ultra Low Emission Vehicle.
SuperCharger or SuperCharged (SC)  A forced-induction system, or its primary component  a rotating mechanism driven mechanically by engine power to provide pressurized air to the intake manifold. Contrast Turbocharger, Ram Air, Naturally Aspirated.
Suspension Lift  The modification of a vehicle's ride height by increasing the vertical distance from the frame (or unibody) to the hubs. It usually results in increased suspension travel, body sway, and approach/breakover/departure angles. It does not affect ground clearance. See Lift. Contrast Body Lift, Tire Lift.
SUT  Sport-Utility Truck. A class of vehicles that generally includes 4-door wagon-body open-bed light trucks, & minivans designed to look like 4-door open-bed light trucks.
SUV  Sport-Utility Vehicle. A class of vehicles that generally includes wagon-body light trucks, & minvans with slightly increased ground clearance and short wheelbase. Some are available with 4WD or AWD.
Suva®  The DuPont name for R-134a. See Refrigerant.
SV CBV  Solenoid Valve Carborator Bowl Vent (carburetor/vacuum)
SVO or SVT  Ford's high-performance division, originally called Special Vehicle Operations, but changed to Special Vehicle Team.
Sw.    Switch
SWAG  (slang) Slightly wild-ass guess.
Swage  1) A connection (usually a soft hose to a rigid nipple) secured by compressing a solid collar past a lip or barb using dies or rollers. Many power steering & A/C hoses are die swaged. 2) The tool used in this process.
SWB    Short Wheel Base
Switch  A device for making, breaking, or changing the connections in an electrical circuit.
SWR  Standing Wave Ratio.
Sys.    System
System  A group of interacting mechanical &/or electrical components serving a common purpose.
T.P.I. Tuned Port Injection
TAC, T.A.C. Thermostatic air cleaner
TACH    Tachometer
TBI Throttle body injection
TBI    Throttle Body Injection
TCC    Torque Converter Clutch
TCM    Transmission or Transaxle Control Module
TCS Transmission controlled spark
TCS    Traction control solenoid
TD    Turbo Diesel
TDC    Top Dead Center
TDI    Turbo Direct Injection
Temp.    Temperature
tg, TG, Turbo glide
th, TH, Turbo hydamatic
THERMAC    Thermostatic Air Cleaner
TI, T.I. Transistor Ignition
TIV    Thermactor Idle Vacuum Valve
tk, Tk, TK Truck
TKS    Throttle Kicker Solenoid
TPI    Tuned Port Injection
TPP    Throttle Position Potentiometer
TPS    Throttle Position Sensor/Switch
TPT    Throttle Position Transducer
TRC, T.R.C. Throttle return control
Tri-five A 1955-56-57 Chevy
Tri-Power Three two barrel carburetors
TS    Temperature Sensor
TSP    Throttle Solenoid Positioner
TV    Thermovalve
TV    Throttle Valve
TVS    Thermal Vacuum Switch
TVS, T.V.S. Thermal vacuum switch
TWC    Three Way Catalyst
U/S    Undersize
UPR Upper
VAC * Vaccum
Vac.    Vacuum
VAF    Vane Airflow
VAPS    Variable Assist Power Steering
VCC    Viscous Converter Clutch
VCRM    Variable Control Relay Module
VIN    Vehicle Identification Number
VM    Vacuum Modulator
VOLT.    Voltage
VOM    Volt/Ohmmeter
VRV    Vacuum Regulator Valve
VSS    Vehicle Speed Sensor
VSV    Vacuum Switching Valve
VVC    Variable Valve Control
VVT    Variable Valve Timing
VVT-i    Variable Valve Timing with intelligence (controlled by the ECM)
W.W.W. Wide white walls
W/ With
W/    With
W/O Without
W/O    Without
WAC    Wide Open Throttle A/C Switch
WB wheel base
WB02    Wide Band Oxygen Sensor
WCFB "Will Carter four barrel" A 4 barrel carburetor made by Carter
Wheel offset (backspace) This is the distance from the rear mounting surface of the wheel to the rear edge of the rim.  Example
WHL wheel
w-motor, W-motor 348 or 409 Chevy engine
WOT    Wide Open Throttle
WOT, W.O.T. Wide Open Throttle
Z-11 The R.P.O. number for the aluminum nosed 427 Impala
Click here to view a sample build sheet
2V
Two (Venturi) Valve (two barrel carburetor)
2v
Two Valve (cylinder head)
2WS
Two Wheel Steer
4EAT
Four speed Electronic Automatic Transmission
4V
Four (Venturi) Valve (four barrel carburetor)
4v
Four Valve (cylinder head)
4WAS
Four Wheel Air Suspension
4WD
Four Wheel Drive
4WS
Four Wheel Steer
16v
Sixteen valve (cylinder head)
AAT
Ambient Air Temperature
ABC
Active Body Control
ABS
Antilock Brake System
A/C
Air Conditioning
ACC
Adaptive Cruise Control
ACC
Automatic Climate Control
accel
Acceleration
accum
Accumulator
accy
Accessory
ACE
Active Cornering Enhancement
ACL
Air cleaner
ACM
Airbag Control Module
ACM
Audio Control Module
ACT
Air Charge Temperature
ADAS
Advanced Driver Assistance System
ADC
Automatic Distance Control
ADL
Automatic Door Lock
AECM
Airbag Electronic Control Module
A/F
Air Fuel Ratio (see also AFR)
AFC
Air Flow Control
AFC
Air Fuel Control
AFR
Air Fuel Ratio (see also A/F)
AGVS
Automated Guided Vehicle System
AHLD
Automatic Headlamp Levelling Device
AHR
Active Head Restraint
AHS
Active Handling System
AIS
Automatic Idle Speed
ALC
Automatic Level Control
ALT
Alternator (see also GEN)
AMM
Air Mass Meter
AMT
Automated Manual Transmission
AOD
Automatic Overdrive
AOS
Automatic Occupant Sensing
API
American Petroleum Institute
APO
Accessory Power Outlets
APP
Accelerator Pedal Position
ARC
Active Roll Control
ARC
Automatic Ride Control
ARS
Automatic Restraint System
ASARC
Air Suspension Automatic Ride Control
ASCD
Auto Speed Control Device
ASF
Audi Space Frame
ASG
Automatic-Shift Gearbox
ASR
Acceleration Slip Regulation
ASTC
Automatic Stability and Traction Control
A/T
Automatic Transmission
ATC
Automatic Temperature Control
ATDC
After Top Dead Center
ATF
Active Transfer Case
ATF
Automatic Transfer Case
ATF
Automatic Transmission Fluid
ATSLC
Automatic Transmission Shift Lock Control
ATTS
Advanced Torque Transfer System
AWD
All Wheel Drive
AYC
Active Yaw Control
BARO
Barometric (pressure)
BAS
Brake Apply Sensor
batt
Battery
BBK
Big Brake Kit
BBV
Brake Booster Vacuum
BCM
Body Control Module
BHP
Brake Horsepower
BLW
Brake Lining Wear
BMAP
Barometric and Manifold Absolute Pressure
BP
Back Pressure
BPA
Brake Pedal Applied
BPA
Bypass Air
BPMV
Brake Pressure Modulator Valve
BPP
Brake Pedal Position
BPW
Base Pulse Width
BTCM
Brake Torque Control Module
BTDC
Before Top Dead Center
BTSI
Brake Transmission Shift Interlock
C3I
Computer Controlled Coil Ignition
CAA
Canadian Automobile Association
CAA
Clean Air Act
CAB
Controller, Antilock Brake
CAC
Charge Air Cooler
CAFC
Company Average Fuel Consumption (Canada)
CAFE
Corporate Average Fuel Economy (USA)
CASE
Cranking Angle Sensing Error
CC
Climate Control
CC
Coast Clutch
CC
Cruise Control
CCD
Chrysler Collision Detection
CCCD
Catalytic Converter Cool-Down
CCD
Computer Controlled Dwell
CCDIC
Climate Control Driver Information Center
CCFL
Cold-Cathode Flourescent Lamp
CCM
Central Control Module
CCM
Chassis Control Module
CCP
Climate Control Panel
CCS
Climate Controlled Seat
CCS
Coast Clutch Solenoid
CDA
Cylinder De-Activation
CDR
Chrysler Diagnostic Readout
CDR
Crash Data Retrieval
CDRV
Crankcase Depression Regulator Valve
CEL
Check Engine Light (see also MIL)
CEAB
Cold Engine Air Bleed
CEMS
Catalyst Efficiency Management System
CEMS
Carbureted Engine Management System
CFI
Central Fuel Injection (replaced with TBI)
CFI
Continuous Fuel Injection
cfm
cubic feet per minute
CG
Center of Gravity
CHMSL
Center High Mounted Stop Lamp
CID
Cubic Inch Displacement
CID
Cylinder Identification
CKP
Crankshaft Position
CL
Closed Loop
CLCC
Closed Loop Carburetor Control
CLS
Coolant Level Switch
CLTBI
Closed Loop Throttle Body Injection
CLNT
Coolant
CMC
Compressor Motor Controller
cmd
Command
cmdd
Commanded
CMFI
Central Multi-port Fuel Injection
CMP
Camshaft Position
CMVSS
Canadian Motor Vehicle Safety Standards
CNG
Compressed Natural Gas
CO
Carbon Monoxide
CO2
Carbon Dioxide
comm
Communication
cond
Condition
const
Constant
COP
Coil On Plug
COP
Computer Operating Properly
CP
Canister Purge
CPC
Camshaft Position Control
CPI
Central Port Fuel Injection
CPP
Clutch Pedal Position
CPS
Cam Profile Switching
CPS
Childseat Postioning Sensor
CPU
Central Processing Unit
CRR
Cool Running Rotor
CS
Charging System
CSC
Commercial Stripped Chassis
CSFI
Central Sequential Fuel Injection
CSI
Compression Sense Ignition
CTD
Content Theft Deterent
CTOX
Continuous Trap Oxidizer
CTP
Closed Throttle Position (switch)
CTS
Coolant Temperature Sensor
CV
Constant Velocity
CVN
Calibration Verification Number
CVRSS
Continuously Variable Road Sensing Suspenion
CVRTD
Continuously Variable Real Time Damping
CVT
Continuously Variable Transmission
CZS
Crash Zone Sensor
DAB
Delayed Accessory Bus
DAB
Driver AirBag (module)
DART
Diagnostic And Reprogramming Tool
dB
Decibels
dBA
decibels on A-weighted scale
DBB
Dual Bed Bead
DBM
Dual Bed Monolith
DC
Direct Current
DC
Duty Cycle
DCCSM
Dual Climate Controlled Seat Module
DCM
Door Control Module
DDM
Driver's Door Module
DDS
Deflection Detection System
DDS
Driver's Door Switch
DE
Drive End
dec
Decrement
DEC
Digital Electronic Controller
DERM
Diagnostic Energy Reserve Module
des
Desired
DFCO
Deceleration Fuel CutOff
DFI
Direct Fuel Injection
DGI
Direct Gasoline Injection
DI
Distributor Ignition
DIC
Driver Information Center
diff
Differential
DIM
Dashboard Integration Module
dis
Disable
DIS
Direct (aka Distributorless) Ignition System (replaced with EI)
disc
Disconnect
DISI
Direct Injection, Spark Ignition
DIST
Distributor
DIY
Do It Yourself
DLC
Data Link Connector
DLC
Diamond Logic Computer
DMCM
Driver Motor Control Module
DMM
Digital MultiMeter
DMSD
Drive Motor Speed and Direction
DOHC
Double Overhead Cam
DNR
Dolby Noise Reduction
DOL
Data Output Line
DPFE
Differential Pressure Feedback EGR
DPI
Dual Plug Inhibit
DRB
Diagnostic Readout Box
DRF
Deactivating Roller Follower
DRL
Daytime Running Lamps
DRR
Digital Radio Receiver
DRW
Dual Rear Wheel
DSCC
Distance Sensing Cruise Control
DSDA
Dual Stage Driver Airbag
DSG
Direct Shift Gearbox
DSI
Dual Stage Inflator
DSM
Driver's Seat module
DSO
Digital Storage Oscilloscope
DSP
Digital Signal Process
DSPA
Dual Stage Passenger Airbag
DSRC
Dedicated Short Range Commnication
DSS
Downshift Solenoid
DSST
Dunlop Self Supporting Tyre
DTC
Diagnostic Trouble Code
DTM
Diagnostic Test Mode
DTR
Digital Transmission Range
DTT
Diesel Transmission Technologies
DVOM
Digital Volt-Ohmmeter
E4OD
Electronic 4-Speed Overdrive
E10
Ethanol 10 percent
E85
Ethanol 85 percent
EA
Electronic Accelerator
EAC
Electronic Air Control (replaced with AIR)
EAIR
Electronic (secondary) Air Injection Reaction
EAS
Electrically Assisted Steering
EAS
Electronic Air Switching
EATC
Electronic Automatic Temperature Control
EBC
Electronic Brake Control
EBCM
Electronic Brake Control Module
EBD
Electronic Brake force Distribution
EBM
Electronic Brake Module
EBP
Exhaust Back Pressure
EBTCM
Electronic Brake and Traction Control Module
EC
Electrical Center
EC
Electronic Control
E&C
Entertainment and Comfort
ECA
Electronic Control Assembly (replaced with PCM)
ECC
Electronic Climate Control
ECD
Electronically Controlled Deceleration
ECI
Extended Compressor at Idle
ECL
Engine Coolant Level
ECM
Electronic Control Module
ECM
Engine Control Module
ECS
Electronic Crash Sensor
ECS
Emission Control System
ECT
Engine Coolant Temperature (Switch, Sensor)
ECU
Electronic Control Unit
EDF
Electric Drive Fan (relay)
EDIS
Electronic Direct Ignition System (replaced with EI)
EDR
Event Data Recorder
EDSR
Electronic Dealer Service (Investigation) Report
EEC
Electronic Engine Control
EEDS
Electric-Electronic Distribution System
EEPROM
Electronically Erasable Programmable Read Only Memeory
EEVIR
Evaporator Equalized Values In Receiver
EFE
Early Fuel Evaporation
EFI
Electronic Fuel Injection
EFTA
Engine Fuel Temperature - Bank 1 Input DEGREES
EFTA V
Engine Fuel Temperature - Bank 1 Input VOLTS
EFTB
Engine Fuel Temperature - Bank 2 Input DEGREES
EFTB V
Engine Fuel Temperature - Bank 2 Input VOLTS
EGC
Electronic Gauge Cluster
EGO
Exhaust Gas Oxygen (replaced with O2S)
EGOG
EGO Ground
EGR
Exhaust Gas Recirculation
EGRBARO
Enable Baro Read instead of EGR pressure
EGRC
Exhaust Gas Recirculation Control
EGRCMDS
EGR Motor Commanded In Steps
EGRMC1
EGR Motor Control Output Command
EGRMC2
EGR Motor Control Output Command
EGRMC3
EGR Motor Control Output Command
EGBMC4
EGR Motor Control Output Command
EGRT
Exhaust Gas Recirculation Temperature (switch)
EGR TVV
Exhaust Gas Recirculation Thermal Vacuum Valve
EGRV
Exhaust Gas Recirculation Vent
EGRVR
EGR Valve Vacuum Control
EGTS
Exhaust Gas Temperature Switch (replaced with EGRT)
EHB
Electro-Hydraulic Brake
EHCU
Electronic Hydraulic Control Unit
EHOC
Electrically Heated Oxidation Catalyst
EHPA
Electro-Hydraulic Power Assist
EHPAS
Electric Hydraulic Power Assisted Steering
EHPS
Electro-Hydraulic Power Steering
EHTWC
Electrically Heated Three Way Catalyst
EI
Electronic Ignition (includes Distributorless Ignition System, formerly DIS)
ELC
Electronic Level Control
EM
Energy Management
EM
Engine Modification
EMAS
Engine Management and Analysis System
EMAT
Electro-Mechanical Automatic Transmission
EMB
Electromagnetic Brakes
EMB
Electro-Mechanical Brake
EMCC
Electronically Modulated Converter Clutch
EMF
ElectroMotive Force (voltage)
EMI
Electromagnetic Interference
EMR
Electronic Module Retard
EMR
Emission Maintenance Reminder
EMS
Engine Management System
EOBD
Enhanced On-Board Diagnostics
EOP
Engine Oil Pressure
EOT
Engine Oil Temperature
EOTF
Engine Oil Temperature Fault Detection
EOT V
Engine Oil Temperature Volts
EP
Exhaust Pressure
EPA
Environmental Protection Agency
EPACT
Energy Policy Act
EPC
Electronic Pressure Control
EPHS
Electrically Powered Hydraulic Steering
EPR
Exhaust Pressure Regulator
EPROM
Erasable Programmable Read Only Memory
EPS
Electric Power Steering
EPS
Electric Power Steering
EPS
Engine Position Sensor
EPT
EGR Pressure Transducer (replaced with PFE)
ERH
Extended Ride Height
ESB
Energy Storage Box
ESB
Expansion Spring Brake
ESC
Electrical Systems Controller
ESC
Electronic Spark Control
ESC
Electronic Suspension Control
ESC
Extended Service Contract
ESCM
Energy Storage Control Module
ESD
Electrostatic Discharge
ESM
EGR System Module
ESM
Electronic Steering Module
ESN
Electronic Serial Number
ESO
Engine ShutOff
ESOF
Electronic Shift On (the) Fly
ESP
Electronic Stability Program
EST
Electronic Spark Timing
ETBE
Ethyl Tertiary Butyl Ether
ETC
Electronic Temperature Control
ETC
Electronic Throttle Control
ETC
Electronic Timing Control
ETCC
Electronic Touch Climate Control
ETR
Electronically Tuned Receiver
ETS
Enhanced Traction System
EUDC
Extra-Urban Driving Cycle
EUDC-LP
Extra-Urban Driving Cycle for Low Power vehicles
EV
Electric Vehicle
EVA
Electronic Vibration Analyzer
EVAP
Evaporative Emission
EVAPCPF
Evaporative Emissions Canister Purge Fault YES/NO
EVAPCV
Evaporative Emissions Canister Purge Vent Control
EVAPCVF
Evaporative Emissions Canister Purge Vent Fault
EVAPPDC
Evaporative Emissions Canister Purge Control %
EVAPPF
Evaporative Purge Flow Input VOLTS
EVIC
Electronic Vehicle Information Center
EVMV
Electric Vapour Management Valve
EVO
Electronic Variable Orifice
EVP
EGR Valve Position (sensor)
EVR
EGR Vacuum Regulator
EVTOP
Enhanced Tactical Vehicle Occupant Protection
EVTM
Electrical & Vacuum Troubleshooting Manual
EWMA
Exponentially Weighted Moving Average
EXH
Exhaust
F4WD
Full Time Four Wheel Drive
FABS
Flexible Auto Body System
FAF
Fan Air Flow
FANDC
Variable Speed Fan Duty Cycle %
FANVARF
Variable Speed Fan Output Fault
FBC
Feedback Carburetor
FC
Fan Control
FC
Friction Curve
FCM
Front Control module
FCP
Fuel Cell Partnership
FCU
Front Control Unit
FCV
Fuel Cell Vehicle
FDBK
Feedback
FDC
Fuel Data Center
FEAD
Front End Accessory Drive (belt)
FED
Federal (except California)
FEDS
Fuel Enable Data Stream
FEDS
Flexible Engine Diagnostic System
FEIC
Fuel Economy Integrated Counter
FET
Field Effect Transistor
FEX
Front Exchanger
FF
Flexible Fuel
FFCRS
Front-Facing Child Restraint System
FFFP
Fuel-Flexible Fuel Processor
FFH
Fuel Fired Heater
FFS
Fine-blanking and Finishing System
FFS
Flexible Fuel Sensor
FFV
Flexible Fuel Vehicle
FFWS
Fuel Filter Water Separator
FI
Fuel Injection
FICM
Fuel Injector Control Module
FIDO
Flame Ionization Detector Optimization
FIM
Fuel Indicator Module
FIPL
Fuel Injection Pump Lever
FIPT
Fuel Inlet Pressure Test
Fl
Front Left
FLI
Fuel Level Indicator Input percent
FLI V
Fuel Level Indicator Input VOLTS
FLO
Fast Light-Off
flr
Floor
FLVV
Fill Limit Vent Valve
FM
Frequency Modulation
FMEM
Failure Mode Effects Management
FMVSS
Federal Motor Vehicle Safety Standards
FP
Fuel Pump
FPCM
Fuel injection Pump Control Module
FPDM
Fuel Pump Driver Module
FPF
Fuel Pump Output Fault
FPI
Fins Per Inch
FPM
Fuel Pump Monitor
FPR
Fuel Pump Regulator
FPRC
Fuel Pressure Regulator Circuit
FPS
Fast Pass Standard
FPSM
Fuel Pump Secondary Monitor
FPV
Ford Performance Vehicles
FR
Front Right
FRACAS
Failure Reporting And Corrective Action System
FRC
Forced
freq
Frequency
frnt
Front
FRP
Fuel Rail Pressure
FRS
Face Recognition System
FRV
First Response Vehicle
FSA
Field Service Action
FSDI
Four-Stroke, Direct Injection
FSI
Fuel Straight Injection
FSS
Forward Sensing System
FSVF
Fuel Solenoid Valve Fault
FSVM
Fuel Solenoid Valve Secondary Monitor
FT
Fuel Trim
FTP
Federal Test Procedure
FTP
Fuel Tank Pressure
FTPT
Fuel Tank Pressure Transducer
FUDC
Federal Urban Driving Cycle
FUELPW1
Injector Pulse Width Bank 1
FUELPW2
Injector Pulse Width Bank 2
FW
Flat Wire
fwd
Forward
FWD
Front Wheel Drive
GA
Gage
GA
Gravitational Acceleration
GAWR
Gross Axle Weight Rating
GCR
Global Concern Report
GCW
Gross Combined Weight
g/cyl
Grams per Cylinder
GCWR
Gross Combined Weight Rating
GDI
Gasoline Direct Injection
GEN
Generator
GENF
Generator Output Fault
GENFDC
Generator Field Control Output
GEM
Gasoline Engine Management
GEM
Generic Electronic Module
GFS
Generator Field Signal
GGT
Gas Guzzler Tax
GHG
GreenHouse Gas
GISMO
Geographic Information System, Mobile
GND
Ground
GOVN
Governor Module
GPCM
Glow Plug Control Module
GPS
Global Positioning System
GS
Garage Shift
g/sec
Grams per Second
GTL
Gas To Liquid
GVW
Gross Vehicle Weight
GVWR
Gross Vehicle Weight Rating
H
Hydrogen
H2DI
Hydrogen Direct Injection
H2O
Water
HAST
High Accelerated Stress Test
HBA
Hydraulic Brake Assist
HBU
Hub Bearing Unit
HC
Hydrocarbons
HCCI
Homogeneous-Charge, Compression Ignition
HCM
Heating Control Module
HCM
Hybrid Control Module
HCU
Hydraulic Control Unit
HCV
Heavy Commercial Vehicle
H/CMPR
High Compression
HD
Heavy Duty
HDC
Heavy Duty Cooling
HDGV
Heavy Duty Gasoline-fueled Vehicle
HDR
High Data Rate
HD-UDDS
Heavy Duty Urban Dynamometer Driving Schedule
HEC
Hybrid Electronic Cluster
HEDF
High Speed Electro Drive Fan (relay or circuit)
HEGO
Heated Exhaust Gas Oxygen (sensor) (replaced with HO2S)
HEGOG
HEGO Ground (circuit)
HEPS
Hydraulic Electric Power Steering
HEUI
Hydraulic-actuated Electronically-controlled Unit Injector
HEV
Hybrid Electric Vehicle
HFC
High Fan Control
HFC
Hydraulic Fading Compensation
HFCF
High Speed Fan Control Fault
HFM
Hot Film Meter
HFP
High Fuel Pump
Hg
Mercury
Hi Alt
Hi Altitude
HICAS
High Capacity Actively Controlled Steering
HID
High Intensity Discharge
HIS
Horizontal Impact Sensor
hist
History
HLDT
Heavy Light-Duty Truck
HLOS
Hardware Limited Operating Strategy
HO
High Output
HO2S
Heated Oxygen Sensor
hp
Horsepower
HPDI
High Pressure Direct Injection
HPL
High Pressure Liquid
HPP
High Pressure Pump
HPS
Head Protection System
HPS
High Performance System
HPV
High Pressure Vapour
HPVS
Heat Pump Ventilation System
HRC
Headlamp Range Control
HSA
Head Side Airbag
HSC
High Swirl Combustion
HSCDS
High-Sensitivity Collision Detection System
HSDI
High-Speed Direct Injection
HSE
High-Speed Enrichment
HSEA
High Solar Energy Absorbing (glass)
HTCM
Heating-ventilation-air-conditioning Thermal Control Module
HTR11
Bank 1 Upstream 02S Heater Control
HTR11F
Bank 1 Upstream 02S Heater Circuit Fault
HTR12
Bank 1 Downstream O2S Heater Control
HTR12F
Bank 1 Downstream O2S Heater Circuit Fault
HTR21
Bank 2 Upstream O2S Heater Control
HTR21F
Bank 1 Downstream O2S Heater Circuit Fault
HTR22
Bank 2 Downstream 02S Heater Control
HTR22F
Bank 1 Downstream O2S Heater Circuit Fault
HTRX1
02S Upstream Heater Control
HTRX2
O2S Downstream Heater Control
HUD
Heads Up Display
HUD
Heads Up Display
HVAC
Heater-Vent-Air Conditioning
HVACM
Heater-Vent-Air Conditioning Module
HVI
High Viscosity Index
HVIL
High Voltage Interlock Loop
HVM
Heater Vent Mondule
HW
Heated Windshield
HWFET
Highway Fuel Economy Test (driving schedule)
HYPAS
Hydraulic Power Assisted Steering
Hz
Hertz
IA
Intake Air
IABM
Integrated AirBag Module
IAC
Idle Air Control
IAFM
Integrated Air Fuel Module
IAFS
Integrated Air Fuel System
IAT
Intake Air Temperature
iATN
International Automotive Technicians Network
IBOB
Intelligent BreakOut Box
IC
Ignition Control
IC
Integrated Circuit
ICA
Injector Cam Actuation
ICC
Intelligent Cruise Control
ICCS
Integrated Chassis Control System
ICDX
Integrated Compact Disc Changer
ICE
Internal Combustion Engine
ICM
Ignition Control Module
ICP
Injection Control Pressure
ICS
Integrated Chassis System
ICWS
Intersection Collision Warning System
ID
Identification
ID
Inside Diameter
IDI
Integrated Direct Ignition
IDIS
International Dismantling Information System
IDM
Ignition Diagnostic Module
IDM
Injector Driver Module
IDS
Integrated Diagnostic Software
IEDIS
Integrated Electronic Distributorless Ignition System
IFES
Integrated Front End System
IFI
Indirect Diesel Injection
IFS
Inertia Fuel Shutoff
IFSM
Integrated Fuel System Module
IGN
Ignition
ILC
Idle Load Compensator
ILEV
Inherently Low Emission Vehicle
illum
Illumination
I/M
Inspection Maintenance
IMA
Integrated Motor Assist
IMDX
Integrated Mini Disc Changer
IMLUT
Inspection/Maintenance Look-Up Table
immo
Immobilizer
IMPR
In-use Monitor Performance Ratio
IMRC
Intake Manifold Runner Control
IMRC F
Intake Manifold Runner Control Fault YES/NO
IMRCM
Intake Manifold Runner Control Monitor Input Bank 1 VOLTS
IMRCM2
Intake Manifold Runner Control Monitor Input Bank 2 VOLTS
IMS
Inductive Magnetic Saturation
IMS
Instant Mobility System
IMSC
Intake Manifold Swirl Control
IMSC F
Intake Manifold Swirl Control Fault
IMT
Intake Manifold Tuning
IMTD
Intake Manifold Temperature Differential
IMTV
Intake Manifold Tuning Valve Control %
IMTVF
Intake Manifold Tuning Valve Fault
in
Inch(es)
inadv
Inadvertant
inc
Increment
INCA
In-Car Aquisition
incand
Incandescent
infl
Inflatable
init
Initial
INJ
Injection
INJ
Injector
INJ1F-8F
Fuel Injector Primary Fault Cylinders 1 thru 8
INJ9F-lOF
Fuel Injector Primary Fault Cylinders 9 and 10
INP
Input
inst
Instant
int
Interior
INT
Integrator (replaced with ST FUEL TRIM)
I/O
In/Out
IOC
Instant Oil Change
I/P
Instrument Panel
IPC
Instrument Panel Cluster
IPEC
Instrument Panel Electrical Center
IPM
Instrument Panel Module
IPM
Integrated Power Module
IPR
Injector Pressure Regulator
IRDS
Independant Rear Drive Suspension
IRQ
Interrupt Request
IRS
Independant Rear Suspension
ISA
Integrated Starter-Alternator
ISAD
Integrated Starter Alternator Damper
ISB
Interact System B
ISC
Idle Speed Control
ISG
Integrated Starter-Generator
ISI
Ion Sensing Ignition
ISO
Interior Systems Optimization
ISO
International Standards Organization
iso
Isolation
ISS
Input Shaft Speed
ITARDA
Institute for Traffic Acccident Research and Data Analysis
ITTB
Idle Time To Boil
ITTR
Inflatable Tubular Torso Restraint
ITS
Idle Tracking Switch
IVC
Integral Vapour Canister
IVCS
Integrated Vehicle Control System
IVI
Intelligent Vehicle Initiative
IVIS
In Vehicle Information System
IVMS
In Vehicle Monitoring System
IVS
Idle Validation Switch
IVSC
Integrated Vehicle Speed Control
i-VTEC
Intelligent Variable (valve) Timing (and lift) Electronic Control
IWC
Inertia Weight Class
JARI
Japan Automotive Research Institute
JTEC
Jeep, Truck Engine Control
JTEC
Joint Transmission-Engine Controller
KAM
Keep Alive Memory
KAPWR
Keep Alive power
KDD
Keyboard Display Driver
kg
Kilogram
kg/h
Kilograms per Hour
kHz
Kilohertz
km
Kilometer
km/h
Kilometers per Hour
km/l
Kilometers per Litre
KOEO
Key On Engine Off
KOER
Key On Engine Running
kPa
Kilopascal
KS
Knock Sensor
KS1 V
Knock Sensor Input Bank 1 VOLTS
KS2 V
Knock Sensor Input Bank 2 VOLTS
kV
Kilovolts
L
Liter(s)
L4
Four Cylinder Inline Engine
LATCH
Lower Anchors and Tethers for CHildren
LB
Long Box, Long Bed
LCD
Liquid Crystal Display
LCM
Lighting Control Module
LDAS
Lane Departure Avoidance System
LDCL
Left Door Control Locking
LDCM
Left Door Control Module
LDDT
Light Duty Diesel Truck
LDGT
Light Duty Gasoline (fueled) Truck
LDM
Lamp Driver Module
LDP
Leak Detection Pump
LDR
Low Data Rate
lduty
Light Duty
LEADER
Low Emissions Advanced Engine Range
LED
Light Emitting Diode
LEP
Light Emitting Polymer
LEV
Low Emissions Vehicle
LF
Left Front
LFC
Lamp Fault Code
LFC
Low Fan Control
LFCF
Low Speed Fan Control Fault
LFWS
Left Front Wheel Speed
LFCS
Low Flow Cooling System
LFP
Low Fuel pump
LGM
Lift Gate Module
LH
Left Hand
LIE
Laterally Inclined Engine
L/M
Litres Per Minute
lm
Lumens
LMD
Left Mid Door
LNG
Liquid Natural Gas
LO
Low
LOMA
Lifter Oil Manifold Assembly
LONGFT1
Long Term Fuel Trim Bank 1 %
LONGFT2
Long Term Fuel Trim Bank 2 %
LOS
Limited Operation Strategy
LPA
Low Pressure Accumulator
LPG
Liquified Petroleum Gas
LPM
Litres Per Minute
LPO
Limited Production Option
LPS
Low Pressure Sensor
LR
Left Rear
LR
Loaded Radius
LRA
Latching Rocker Arm
LRD
Left Rear Door
lrn
Learn
LSD
Limited Slip Differential
LSEGR
Linear Solenoid Exhaust Gas Recirculation
LSP and BV
Load Sensing Proportioning and Bypass Valve
LSUV
Luxury Sport Utility Vehicle
LT
Left
LT
Long Term (Fuel Trim)
LTA
Low Temperature Aftercooling
LTD
Long-Travel Dampened (clutch)
LTPI
Low Tyre Pressure Indicator
LTPWS
Low Tyre Pressure Warning System
LUS
Lock-Up Solenoid (see TCC)
LV8
Load Variable 8 Cylinder
LVDT
Linear Variable Differential Transducer
LVL
Level
LWB
Long WheelBase (see LB)
MAF
Mass Air Flow
malf
Malfunction
MALL
Multifunction Alarm Lighting and Locking
MAN
Manufacturer
MAP
Manifold Absolute Pressure
Map
Large folded piece of colourful paper
MAT
Manifold Air Temperature
MC
Measuring Core
MC
Mixture Control
MCM
Message Center Module
MCNU
Multiband Configurable Networking Units
MCU
Microprocessor Control Unit
MD
Mini Disc
MD
Modulated Displacement
MDP
Manifold Differential Pressure
MDS(2)
Mopar Diagnostic System
MDX
Mini Disc Changer
MECS
Mazda Electronic Control System
med
Medium
MEM
Memory
MEMCAL
Memory Calibration
MFC
Medium Speed Fan Control ON/OFF
MFCF
Medium Speed Fan Control Fault YES/NO
MFI
Multiport Fuel Injection
MFI
Multi Function Indicator
MGMT
Management
MIC
Mechanical Instrument Cluster
MID
Midrange
MID
Monitor Identification
MIL
Malfunction Indicator Lamp
MIN
Minimum
MIN
Minute
MIN
Mobile Identification Number
MIP
Mixer Inlet Pressure
ML
Manual Longitudinal
MLP(s)
Manual Lever Position (sensor)
mm
Millimetre
mm3
Cubic Millimetre(s)
MMC
Manifold Mounted Converter
mmhg
Millimeters of mercury
MMM
Memory Mirror Module
MMT
Methylcyclopentadienyl Manganese Tricarbonyl
mod
Module
mon
Monitor
MPa
Megapascal
MPFI
Multiport Fuel Injection
ms
Millisecond
MSFF
Miles Since First Fail
MSLF
Miles Since Last Fail
MSM
Memory Seat Module
MSO
Mixed Signal Oscilloscope
MSRP
Manufacturers Suggested Retail Price
MST
Manifold Surface Temperature
MSVA
Magnetic Steering Variable Assist
M/T
Manual Transmission/Transaxle
MTBE
Methyl Tertiary Butyl Ether
MTBF
Mean Time Between Failures
MTV
Manifold Tuning Valve
MV
Megavolt
mV
Millivolt
MVLPS
Manual Valve Lever Position Sensor
MVSA
Motor Vehicle Safety Act
MVSS
Motor Vehicle Safety Standards
MY
Model Year
NAAO
North American Automotive Operations
NAES
North American Export Sales
NAICC
Navigation-Aided Intelligent Cruise Control
NATS
Nissan Anti-Theft System
NC
Normally Closed
NCAP
New Car Assessment Program
NDH
Navigation Display Head
NEG
Negative
NEU
Neutral
NFF
No Fault Found
NG
Natural Gas
NGS
New Generation STAR (Self Test Automatic Readout)
NGSC
Next Generation Speed Control
NGTP
Next Generation Telematics Protocol
NGV
Natural Gas Vehicle
NGV
New Generation Vehicle
NGVM
Natural Gas Vehicle Module
NHTSA
National Highway Traffic Safety Administration
NI
Neutral Idle
NiMH
Nickel Metal Hydride
NLGI
National Lubricating Grease Institute
N-m
Newton Meters
NO
Normally Open
NOx
Nitrogen Oxides
NoVRAM
Non Volatile Random Access Memory
NPF
No Problem Found
NPTC
National Pipe Thread Coarse
NPTF
National Pipe Thread Fine
NSBU
Neutral Safety Back Up
NV
Night Vision
NVH
Noise, Vibration and Harshness
NVLD
Natural Vacuum Leak Detection
NVRAM
Non Volatile Random Access Memory
NYCC
New York City Cycle
O2
Oxygen
O2S
Oxygen Sensor
OAD
Overrunning Alternator Decoupler
OAP
Overrunning Alternator Pulley
OASIS
Online Automotive Service Information System
OASIS
Organization for the Advancement of Structured Information Standards.
OBD
On Board Diagnostics
OBD II
On Board Diagnostics, Generation 2
OC
Oxidation Catalyst Only
OCC
Output Circuit Check
OCR
Oil Control Ring
OCS
Occupant Classification Sensor
OCS
Opportunity Charge Station
OD
Outside Diameter
OD
Overdrive
ODM
Output Drive Module
ODO
Odometer
OE
Original Equipment
OEM
Original Equipment Manufacturer
OHC
Overhead Camshaft
OL
Open Loop
OLED
Organic Light Emitting Diode
OPR
Over Pressure Relief
ORC
Oxidation Reduction Converter
ORC
Occupant Restraint Controller
ORVR
On-board Refueling Vapour Recovery
OSC
Output State Check
OSC
Output State Control
OSGI
Open-Service Gateway Interface
OSS
Output Shaft Speed
OTC
Overhead Trip Computer
OTIS
Overhead Travel Information System
OTM
Output Test Monitor
PAB
Passenger Air Bag
PADS
Passenger Airbag Disarm Switch
PAG
Polyalkylene Glycol
PAG
(Ford) Premier Automotive Group
PAIR
Pulsed Secondary Air Injection
PASE
PAssive Start and Entry system
PASM
Porche Active Steering Management
PASS
Passenger
PASS
Personalized Automotive Security System
PATS
Passive Anti-Theft System
PB
Power Brakes
PC
Pressure Control
PCB
Printed Circuit Board
PCI
Programmable Communications Interface
PCI
Programmable Controller Interface
PCM
Power Control Module
PCM
Powertrain Control Module
PCS
Pre-Crash Sensor
PCS
Pressure Control Solenoid
PCV
Positive Crankcase Ventilation
PDC
Park Distance Control
PDC
Parts Distribution Center
PDC
Power Distribution Center
PDS
Passenger Door Switch
PDS
Portable Diagnostic Software
PDV
Parcel Delivery Van
PEB
Power Electronics Bay
PEM
Proton Electric Membrane
PEMFC
Proton Exchange Membrane Fuel Cell
PEP
Peripheral Expansion Port
PFE
Pressure Feedback EGR
PFI
Port Fuel Injection
PFM
PDS File Manager
PFS
Purge Flow Sensor
PHEV
Plug-in Hybrid Electric Vehicle
PHT
Parallel Hybrid Truck
PID
Parameter Identification
PIM
Power Inverter Module
PIP
Profile Ignition Pickup (replaced with CKP)
PKE
Passive Keyless Entry
PLL
Phase Locked Loop
PM
Permanent Magnet
PMD
Pump Mounted Driver
PMV
Pressure Modulator Valve
P/N
Part Number
PNP
Park/Neutral Position
POA
Pilot Operated Absolute
pos
Position
POS
Positive
POT
Potentiometer
P-PC
Pocket Personal Computer
ppm
Parts Per Million
PPS
Passenger Presence Sensor
PRNDL
Park Reverse Neutral Drive Low
PROM
Programmable Read Only Memory
PROX
PReferential OXidation
PS
Power Steering
PSA
Pressure Switch Assembly
PSCM
Passenger Seat Control Module
PSCM
Power Steering Control Module
PSD
Power Sliding Door
psgr
Passenger
psi
Pounds Per Square Inch
psia
Pounds Per Square Inch Absolute
psig
Pounds Per Square Inch Gauge
PSIR
Passenger Supplemental Inflatable Restraint
PSM
Passenger Seat Module
PSOM
Programmable Speedometer/Odometer Module
PSP
Power Steering Pressure
PSV
Public Service Vehicle
PTC
Pending Trouble Code
PTC
Positive Temperature Coefficient
PTO
Power Takeoff
PTOX
Periodic Trap Oxidizer
PTU
Part Throttle Unlock
PWM
Pulse Width Modulation
PWR
Power
PZEV
Partial Zero Emision Vehicle
PZM
Platform Zone Module
QDM
Quad Driver Module
QDR
Quality, Durability, Reliability
QVM
Qualified Vehicle Modifier
R/A
Resume or Accelerate
RABS
Rear Antilock Brake System
RAC
Remote Accessory Controller
RAM
Random Access Memory
RAM
Ride Air Module
RAM
Remote Anti-theft Module
RAP
Retained Access Power
RAV
Remote Activation Verification
RBC
Rotary Blade Coupling
RCC
Rear Climate Control
RCC
Remote Climate Control
RCM
Restraint Control Module
RCDLR
Remote Control Door Lock Receiver
RDCM
Right Door Control Module
RDM
Rear Door Module
RDS
Radio (broadcast) Data System
RDS
Radio Display System
rec
Receive
recal
Recalibrate, Recalibration
RECIS
Remote Entry Control and Immobilizer System
REDOX
Reduction Oxidation Catalytic Converter
REEGR
Rotary Electric EGR
REF
Reference
RESC
Remote Emergency Satellite Unit
REX
Rear Exchanger
RF
Radio Frequency
RF
Right Front
RFA
Remote Function Actuator
RFF
Roller Finger Followers
RFI
Radio Frequency Interference
RFID
Radio Frequency Identification
RFWS
Right Front Wheel Speed
RH
Right Hand
RIM
Radio Interface Module
RIM
Rear Integration Module
RKE
Remote Keyless Entry
Rly
Relay
RM
Relay Module
RMD
Right Mid Door
ROM
Read Only Memory
RPA
Rear Parking Assist
RPM
Remote Power Module
RPM
Revolutions Per Minute
RPO
Regular Production Option
R&R
Remove and Replace
RR
Right Rear
RRD
Right Rear Door
RSA
Rear Seat Audio
RSC
Roll Stability Control
RSE
Roadside Equipment
RSS
Reverse Sensing System
RSS
Road Sensing Suspension
R/T
Road/Track
RT
Right
RTC
Real-Time Clock
RTD
Real Time Dampening
RTN
Return
RTT
Reconfigurable Telltale
RTTP
Rotunda Technician Tool Program
RTV
Room Temperature Vulcanizing
RV
Recreational Vehicle
RVAC
Rear Video/Audi/HVAC Module
RVP
Reid Vapour Pressure
RWAL
Rear Wheel Anti-lock
RWD
Rear Wheel Drive
RWS
Rear-Wheel Steer
S4WD
Selectable Four Wheel Drive
SAE
Society of Automotive Engineers
SAF
Stabilized Aluminum Foam
SAS
Side Auxiliary Sensor
SATC
Semi-Auto Temperature Control module
SAVDAS
Stand-Alone Vehicle Data Aquisition System
SAW
Spark Angle Word
SB
Short Box, Short Bed
SBDS
Service Bay Diagnostic System
SBEC
Single Board Engine Controller (replaced with PCM)
SBM
Standard Body Module
SBS
Supercharger Bypass Solenoid
SBT
Serial Bus Traveller
SC
Supercharger
SCA
Supplemental Coolant Additive
SCB
Supercharger Bypass
SCCA
Sports Car Club of America
SCI
Serial Communications Interface
SCIL
Steering Column/Instrument panel Lighting
SCM
Seat Control Module
SCP
Standard Corporate Protocol
SCS
Side Crash Sensor
SCTM
Seatbelt Timer Control Module
SCV
Speed Controlled Volume
SDARS
Satellite Digital Audio Radio System
SDL
Serial Data Link
SDM
Sensing and Diagnostic Module
SDRS
Satellite Digital Receiver System
SDS
Satellite Discriminating Sensor
SDS
Shock Dampening System
SDV
Spark Delay Valve
SEFI
Sequential Electronic Fuel Injection (replaced with SFI)
SEMA
Specialty Equipment Market Association
SEO
Special Equipment Option
SES
Service Engine Soon (replaced with MIL)
SFI
Sequential (multiport) Fuel Injection
SGCM
Starter/Generator Control Module
SHO
Super High Output
SI
System International
SIAB
Side Impact Air Bag
SIACM
Side Impact Air Bag Control Module
SIG RTN
Signal Return
SIL
Shift Indicator Lamp
SIR
Supplemental Inflatable Restraint
SIS
Side Impact Sensor
SKIM
Sentry Key Imobilizer Module
SLB
Smart Junction Box
SLA
Short/Long Arm suspension
SMCC
Stepper Motor Cruise Control
SMEC
Single Module Engine Controller (replaced with PCM)
SMPI
Sequential Multi-Port Injection
SNSR
Sensor
SO2
Sulphur Dioxide
SOC
State Of Charge
SOD
Side Object Detection
SOH
State of Health
sol
Solenoid
S/P
Series/Parallel
SP
Splice Pack
SPD
Speed
SPI
Serial Peripheral Interface
SPL
Smoke Puff Limiter
SPS
Service Programming System
SPS
Speed Signal
SPO
Service Parts Operations
SPOUT
Spark Output
SPRK_ACT
Spark Advance Actual
SPS
Service Programming System
SRC
Selective Ride Control
SRG
Solar-Reflective Glass
SRI
Service Reminder Indicator
SRI
Short Ram Intake
SrPP
Self-reinforced PolyPropylene
SRS
Supplemental Restraint System
SRW
Single Rear Wheel
SS
Shift Solenoid
SS
Speed Signal
SSM
Suspension Steering Module
SSS
Speed Sensitive Steering
SSV
Shift Solenoid Valve
ST
Scan Tool
ST
Short Term (Fuel Trim)
STAR
Self Test Automatic Readout (tester)
STAR
Stolen Auto Recovery System
STC
Snap To Connect
STC
Step Timing Control
stdby
Standby
STI
Self Test Input
STID
Station Identification
STL
Service Transmission Lamp
STO
Self Test Output
STS
Service Technicians Society
SULEV
Super Ultra Low Emission Vehicle
SUV
Sport Utility Vehicle
SVO
Straight Vegetable Oil
SVS
Service Vehicle Soon
SVT
Special Vehicle Team
S/W
Software
sw
Switch
SWB
Short WheelBase (see SB)
SWC
Steering Wheel Controls
SWPS
Steering Wheel Position Sensor
SWS
SideWall tension Sensor
SXR
Send and Receive
syn
Synchronize
sys
System
TAB
Thermactor Air Bypass (replaced with AIRB)
TAC
Throttle Actuator Control
TACH
Tachometer
TACM
Throttle Actuator Control Module
TAD
Thermactor Air Divert (replaced with AIRD)
TAP
Transmission Adaptive Pressure
TAS
Trap Alert System
TB
Throttle Body
TBC
Truck Body Controller (or Computer)
TBI
Throttle Body Fuel Injection
TC
Transmission Control
TC
Turbocharger
TCC
Torque Converter Clutch
TCCS
Toyota Computer Controlled System
TCIL
Transmission Control Indicator Lamp
TCM
Transmission Control Module
TCS
Traction Control System
TCS
Transmission Control Switch
TDC
Top Dead Center
TDI
Toyota Direct Ignition
TED
Thermo Electric Device
tele
Telescope
TEMP
Temperature
TFI
Thick Film Integrated (replaced with DI)
TFP
Transmission Fluid Pressure
TFT
Transmission Fluid Temperature
TGS
Top Gear Switch
THEMIS
Thermal Management Intelligent System
THM
Turbo Hydra-Matic
THS
Transmission Hydraulic Switch
TID
Test Identification
TIIS
Thermal Imaging Inspection Station
TIM
Tyre Inflation Module
TIM
Tyre Inflation Monitor
TIS
Techline Information System
TOC
Transmission Oil Cooler
torq
Torque
TOT
Transmission Oil Temperature
TP
Throttle Position
TPA
Terminal Positive Assurance
TPI
Tuned Port Injection
TPMS
Tyre Pressure Monitor System
TPS
Throttle Position Sensor
TR
Transmission Range
T-RAC
Trailer Rotating Air Chamber
trans
Transmission/Transaxle
TRDU
Trailer Remote Diagnostic Unit
TRS
Transmission Range Sensor
TSA
Thorax Side Airbag
TSB
Technical Service Bulletin
TSI
Two Speed Idle
TSS
Transmission Speed Sensor
TSS
Turbine Shaft Speed
TT
Telltale Lamp
TTM
Tilt and Telescope Module
TTS
Transmission Temperature Switch (replaced with TOT)
TV
Television
TV
Throttle Valve
TVAM
Televison Antenna Module
TVR
Turbine Vane Regulator
TVRS
Television and Radio Suppression
TVS
Thermal Vacuum Switch
TVV
Thermal Vacuum Valve
TWC
Three Way Catalyst
TWC+OC
Three Way Catalyst + Oxidation Catalyst
twtr
Tweeter
TXV
Thermal Expansion Valve
UASID
Units And Scaling Identification
UART
Universal Asynchronous Receiver-Transmitter
UD
Underdrive
UDDS
Urban Dynamometer Driving Schedule
U/H
Underhood
U/HEC
Underhood Electrical Center
UIDI
Up-Integrated Direct Ignition
ULEV
Ultra Low Emissions Vehicle
ULSD
Ultra Low Sulphur Diesel
UMTS
Universal Mobile Telecommunications System
unlk
Unlock
USCAR
United States Council for Automotive Research
UTD
Universal Theft Deterrent
UTQG
Uniform Tyre Quality Grading
V
Volts
V2G
Vehicle to Grid
VAC
Vacuum
VAC
Vehicle Access Code
VACS
Vehicle Access Control System
VAF
Vane Air Flow
VAF
Volume Air Flow
VAPS
Variable Assist Power Steering
VAPS
Virtual Automotive Prototyping System
VASCO
Vehicle Application-Specific Computer
VAT
Vane Air Temperature (replaced with IAT)
VAT
Visual Authoring Tool
VATS
Vehicle AntiTheft System
VB
Valve body
VCC
Viscous Converter Clutch
VCI
Vehicle Communication Interface
VCIM
Vehicle Communication Interface Mode
VCL
Vehicle Communication Link
VCM
Variable Cylinder Management
VCM
Vehicle Communication Module
VCM
Vehicle Control Module
VCRM
Variable Control Relay Module
VCT
Variable Camshaft Timing
VDCS
Vehicle Dynamics Control System
V dif
Voltage Difference
VDIS
Vehicle Diagnostic Information System
VDM
Vehicle Dynamics Module
VDM
Vehicle Dynamics Monitor
VDOT
Variable Displacement Orifice Tube
VDP
Vehicle Dynamics Processor
VDR
Vehicle Data Recorder
VDR
Vehicle Dealer Recorder
VDS
Valve Deactivation System
VDV
Vacuum Delay Valve
VECI
Vehicle Emission Control Information
VEDR
Vehicle Event Data Recorder
veh
Vehicle
vel
Velocity
ver
Version
vert
Vertical
VES
Variable Effort Steering
VF
Vacuum Flourescent
VGT
Variable Geometry Turbocharger
VIC
Virtual Image Cluster module
VICS
Vehicle Information Communication System
VIIC
Vehicle Infrastructure Integration Consortium
VIN
Vehicle Identification Number
VIP
Vehicle Intrusion Protection
VIU
Vehicle Interface Unit
VLCM
Variable Load Control Module
VLR
Voltage Loop Reserve
vlv
Valve
VMM
Vehicle Measurement Module
VMRS
Vehicle Maintenance Reporting System
VMV
Vacuum Modulator Valve
VMV
Vapour Management Valve
VNT
Variable Nozzle Turbine
VNT
Variable Nozzle Turbocharger
VOTM
Vacuum Operated Throttle Modulator
VPWR
Vehicle Power
VR
Vacuum Regulator
VREF
Voltage Reference
VRLA
Valve Regulated Lead Acid
VRV
Vacuum Reducer Valve
VRIS
Variable Resonance Induction System
VS
Variable Speed
VSC
Vehicle Stability Control
VSES
Vehicle Stability Enhancement System
vspd
Vehicle speed
VSS
Vehicle Speed Sensor
VSV
Vacuum Solenoid Valve
VTA
Vehicle Theft Alarm
VTD
Vehicle Theft Deterrent
VTEC
Variable (valve) Timing (and lift) Electronic Control
VTSS
Vehicle Theft Security System
VVT-i
Variable Valve Timing with Intelligence
VVTL-i
Variable Valve Timing and Lift with Intelligence
w/
With
WAC
Wide Open Throttle A/C Cutoff
warn
Warning
W/B
Wheelbase
WCF
Wireless Communication Framework
WDS
Workbay Diagnostic System
WDS
Worldwide Diagnostic System
WGC
Wastegate Control
WHL
Wheel
WIF
Water In Fuel (sensor)
w/o
Without
WOT
Wide Open Throttle
W/P
Water Pump
WSM
WorkShop Manual
WSS
Wheel Speed Sensor
WU-OC
Warmup Catalyst with Oxidation Catalyst
WU-TWC
Warmup Catalyst with Three Way Catalyst
WVO
Waste Vegetable Oil
WVVWS
Wireless Vehicle to Vehicle Warning System
X-valve
Expansion Valve
xVDS
Extended Vehicle Diagnostic System
ZEV
Zero Emission Vehicle