Off Road & Automotive Terms

Glossary of abbreviations and terms used in off road and automotive technology. Use the form below to locate definitions. Where a word may have multiple uses provide a topic entry to limit values returned. Leave either Term or Topic blank to broaden searches.


61 Relevant term(s) found

A580Model of Automatic Transmission
ABSAnit-lock Bracking System, sometimes referred to as Anti-Skid Braking System, is safety system that keeps the wheels of a vehicle in tractional contact with the ground. Without ABS, it is frequently too easy to lock up wheels (stop wheel rotation) in a reduced traction environment such a wet road. Once locked up the wheels will skid and provide little or no control.

On dry and wet pavement ABS often improves braking performance, shortening stopping distance. On looser surfaces such as, loose gravel, mud or snow stopping distances are often longer.

ABS was the first of several brake and stability safety enhancements. Follow on technologies include electronic brake force distribution (EBD) and Electronic Stability Program (ESP) alternately known as Electronic Stability Control or ESC.

ABS PumpPump that provides pressure to drive the Ani-lock Braking System (ABS).
ABS ValveControls pressure to the brakes in an Anit-Lock Brake System (ABS). Releases if it senses a lock condition.
APIAmerican Petroleum Institute
API GLPerformace designation for gear oils. The GL rating is not a viscosity index but a set of performance requirements based on load and geometry such as flat or hypoid meshing.
API Service ClassificationTwo letter designation certifying performance of the oil product. Use oil of the manufacture’s recommended API Service Classification when performing an oil change.
ASDAutomatic Shut Down – Part of the security system that shuts the engine down in the event it believes it should not be on.
AW additivesAntiwear additives, in oils are part of an additive package to reduce wear from metal to metal contact.
AWDAll Wheel Drive. A dynamic power distribution system that applies power from the engine to all wheels based on traction.
carrierWith respect to differentials, a carrier is the housing that the ring gear is attached to and contains the side gears and differential gearing.
DHSDymanic Handling System – An active mechanism that controls body roll while maintaining ride quality. Found on upper end SUVs (such as the WJ Grand Cherokees, 2007 and after), it sits between the anti-roll bar and wheel suspension. Taking real time information such as steering angle, lateral acceleration and vehicle speed the system controls the amount of roll correction exerted by the anti-roll bar.
DTCDiagnostic Trouble Codes, are available through the vehicle’s ODB/ODB-II interface. They document specific operating parameters outside normal operation of the vehicle. Also see: Individual DTC Codes
EATXElectronic Automatic Transaxle – Electronically controlled transmission, works in conjunctoin with a TCM which is attached to the transmission and provides actuation of gear selection based on driver input and vehicle computer.
EATX RelayRelay that powers the Transmission Cotrol Module (TCM). The TCM is resposible for gear selection based on driver input and vehicle computer. On non-TCM transmissions, gear selection is made typically on driver input and haudralicly implemented control circuits.

Also see: TCM
EBDElectronic Brake Distribution
EBLElectric Back Light – This is the rear window in glass defogging element (refered to as a light.)
EP additivesExtreme Pressure Additives, with respect to oils, are compounds that help lubricants reduce wear in parts that are subjects to high pressure, gear face to gear face contact under load such as gear boxes and differientials.
ESC Electronic Stability Control, an active system that evaluates wheel speed, steering position and engine sensor data to determine if the vehicle is in traction or out of traction and adjust by applying brakes at one or more wheel to reacquire traction. The system sometime includes input from inertial sensors. System may also referred to as ESP.
ESP Electronic Stability Program, an active system that evaluates wheel speed, steering position and engine sensor data to determine if the vehicle is in traction or out of traction and adjust by applying brakes at one or more wheel to reacquire traction. The system sometime includes input from inertial sensors. System may also referred to as ESC.
FCDMFinal Control Drive Module
FCMForward Control Module
FOBIKFrequency Operated Button Ignition Key (FOBIK)
FPSFuel Pressure Sensor is located on the Fuel Rail and reports the pressure provided to injectors. Lower pressures deliver less fuel while higher pressure delivers more.
Full Time 4WDFull Time 4WD loosely links the front and rear axles togther via differential (sometimes called the center diff) in place of a transfer case. Like Part time 4WD, full time provides a high and low gear range and is capable of rough trail and moderate wheeling. Performance is improved if the center diff is lockable.
Full Time AWDMore of a handling feature for poor road conditions (rain and light snow). Typically there is no low range setting and not suitable for aggressive trails.
FWDFour wheel drive, a drive system that applies power to all four wheels regardless of traction. Should a wheel have no traction it will slip but only as much as the wheel with the most traction.
GDIGDI stands for Gasoline Direct Injection and is a combustion chamber fuel delivery system that injects the fuel directly into the cyclinder rather than at the intake channel such as Multipoint Fuel Injection.

Also see: Multiport Fuel Injection
hypoidPretaining to gear geometry where two bevel gears in meshed configuration with out intersecting axis. Hypoids are often used in differentials (ring and pinion set). Hypoid gears have the advantage of higher speed resuctions, have smoother meshing resulting in less vibration.
IODIgnition Off Draw – Circuit provided with current even when the key switch is in the off position. Circut typically is used for memory devices (seats, latched engine data and radio settings.)
Lincoln locker Informal term for a spool created by welding the spider gears in an open differentical. With the spider grears immobilized the side gears which drive axles shafts to the wheels must turn at the same speed as the carrier.
locking differentialA type of differential that reduces wheel spin by turning both passenger and driver side wheels at the same speed when engaged. In some designs the effect is a solid axle from wheel to wheel is formed. While engaged, the locker acts like a spool. Engagement schemes can be manual or automatic.
LSWith respect to differentials, LS stands for limited slip. This type of differential limits the amount of wheel slip when one wheel looses traction. Limited slip differentials when used in a front axles allow for easier steering than locked axles when engaged because there is some looseness retained in the LS.
MAFMass Air Flow – Sensor located immediately down stream from thottle body and measure amouunt of air drawn into engine. Valued used by Powertrain Control Module (PCM) which calculates required fuel for a complete burn.

Also see: MAP
MAPManifold Absolute Pressure – Sensor located at intake manifold that measures vacuum and is used by Prowertrain Control Module (PCM) along with Throttle position to calculate fuel delivery for complete burn and advancement of spark timing. (Also see MAF)

Also see: MAF
Multiport Fuel InjectionConventional fuel injection technology that delivers fuel under presssure to the cyclinder intake channel. A more recent technology, seeing rapid adoption is Gasoline Direct Injection (GDI) which operates at an even high pressure and delivers directly into the combustion chamber.
OBD-IIOn-Board Diagnostics 2 (also written as ODB2) is the self-diagnostics system available in most vehicles manufactured since the mid-1990s and reports on status of vehicle subsystems via the use of Diagnostic Trouble Codes (DTC). ODB-II is a further standardization and expansion of the reporting data set over ODB-I (or just ODB.)

Also see: DTC
OBD2On-Board Diagnostics 2 (ODB-II) is the self-diagnostics system available in most vehicles manufactured since the mid-1990s and reports on status of vehicle subsystems via the use of Diagnostic Trouble Codes (DTC). ODB-II is a further standardization and expansion of the reporting data set over ODB-I (or just ODB.)

Also see: DTC
OCMOccupant Restraint Controller – Typically refered to the SRS control module (Suplimental Restraint System is an electronic module that includes the seat belts, airbags, collision sensors)

Also see: SRS
open differentialA type of differential common to almost all passenger cars. An open differential sends power to the wheel most free to rotate. As long as traction is not lost this type of differential is excellent as it sends power smoothly in a turn to the outboard wheels which are rotating more than the inner.
ORCOccupant Restraint Controller – Monitors and controls safety systems such as the seat belts and airbags.

Also see: SRS
Part Time 4WDManually engaged through a transfer case (4WD Hi or Low) when driving over rough terrain including, mud, loose gravel and snow. When engaged both front and rear axles are mechanically linked through the transfer case. Effectiveness is encreased with lockers as little to no power is lost in wheel spin. Of the 4WD/AWD implementations this is the most traditional and in competent hand the most potent. Part time 4WD must not be engaged on pavement or other high traction surface as this can severely damage it.
PCMPowertrain Control Module – Intigrated control of the engine and transmision (see ECU/ECM & TCU.)
PDCPower Distribution Center
RingAlso refered to as the ring gear or crown. Is attached to the differiencial carrier and meshes with the pinion gear which is connected to and driven by the drive shaft.
SAESociety of Automotive Engineers
SAE J306Standards document for gear oil viscosity
SCMSteering Control Module
side gearsThe two gears in the differential carrier that connect the axle shafts to the differential.
SKREEM Security Key Remote Module
SLAShort and Long Arm – The portion of a vehicle suspension system connecting the wheel hub assembly to the chassis. The setup allows for vertical wheel movement and is comprised of two horizontal A arms, the upper typically shorter than the lower to produce negative camber as the wheel rises relative the body. The configuration is sometime referred to as double wishbone.
spider gearsContained within the differiencial carrier, there are typically 2 or 4 spider gears that mesh with the 2 side gears. The spiders provide an open differential with the loose coupling between either side of the axle. Spiders are also know as pinion gears (plural) which can be confusing as these differ from the pinion in the ring and pinion.
spoolIn reference to differentials, a spool connects passenger and driver sides axles creating essential a solid axle from wheel to wheel. The effect is wheels at either side turn in unison. This adversely impacts steering on high traction surfaces such as drive pavement.
SRSSuplimental Restraint System – Often referred to as the Airbag system. This is the safety device that deploys in the event of accident. A dash light that remains on after start of the vehicle indicates an issue with SRS.
T-CaseShort for transfer case. It is the device that splits the drive line providing for a front and rear drive shaft
TCMTransmission Control Module
TPMSTire Pressure Monitoring System, alerts driver via dash light to under inflated tire condition.
TPSThrottle Position Sensor – Sensor located in the Throttle Body that reports how open the throttle is. Provides values to the Powertrain Control Module (PCM) in conjunction with Manifold Absolute Pressure (MAP) to detirmine fuel needed for complete burn and spark advance.

Also see: MAP
VECIStands for Vehicle Emission Control Information. Federal & California laws mandate this information be affixed to the body of the vehicle (information is on a sticker).
viscosityA measure of a fluid’s resistence to flow. Thicker , slower moving fluids have a higher viscosity index, thinner or fast moving fluids have a lowwer index.
WCMWireless Control Module