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Automotive Terms and Acronyms

A summary of acronyms used in OBD system diagnostics.
AFR - Air Fuel Ratio

Assembly Line Diagnostic Link. Former name for GM (only) Data Link Connector, the connector socket into which the scan tool plug is inserted; sometimes used to refer to any pre-OBD II computer signals

CAN - Controller Area Network

C.A.R.B. - California Air Resources Board

CEL - Check Engine Light

CFI - Continuous Fuel Injection

CO - Carbon Monoxide

DLC - Data Link Connector

Driving Cycle - A specific sequence of start-up, warm-up and driving tasks that tests all OBD II functions

DTC - Diagnostic Trouble Code

ECM - Engine Control Module

ECT - Engine Coolant Temperature

EEC - Electronic Engine Control

EEPROM or E2PROM - Electrically Erasable Programmable Read Only Memory

EFI - Electronic Fuel Injection

EGR - Exhaust Gas Recirculation

EMR - Electronic Module Retard

EPA - Environmental Protection Agency

ESC - Electronic Spark Control

EST - Electronic Spark Timing

FLI - Fuel Level Indicator

HC - Hydrocarbons

HEI - High Energy Ignition

O2S - Oxygen Sensor

IAT - Intake Air Temperature

ISO 9141 - International Standards Organization OBDII communication mode, used by Chrysler and most foreign cars. One of three hardware layers defined by OBD II

J1962 - SAE-established standard for the connector plug layout used for all OBD II scan tools

J1978 - SAE-established standard for OBD II scan tools

J1979 - SAE-established standard for diagnostic test modes

J2012 - SAE-established standard accepted by EPA as the standard test report language for emission tests

MAF - Mass Air Flow

MAP - Manifold Absolute Pressure

MAT - Manifold Air Temperature

MFG - Manufacturer

MIL - Malfunction Indicator Light. The "Check Engine Light" on your dash.

NO2 - Nitrous Oxide

O2 - Oxygen

OBD - On-Board Diagnostics

OBDII or OBD II - Updated On-Board Diagnostics standard effective in cars sold in the US after 1-1-96

Parameters - Readings on scan tools representing functions measured by OBD II and proprietary readings

PCM - Powertrain Control Module

PCV - Positive Crankcase Ventilation

PID - Parameter ID

Proprietary Readings - Parameters shown by on-board computers which are not required by OBD II, but included by manufacturer to assist in trouble-shooting specific vehicles.

PTC - Pending Trouble Code

RPM - Revolutions Per Minute

SAE - Society of Automotive Engineers

Scan Tool - Computer based read-out equipment to display OBD I & OBD II parameters

SES - Service Engine Soon (see MIL)

SFI - Sequential Fuel Injection

Stoichiometric (stoi'chi·o·met'ric) Ratio - Theoretical perfect combustion ratio of 1 part gas to 14.7 parts air

TBI - Throttle Body Injection

TPI - Tuned Port Injection

TPS - Throttle Position Sensor

VAC - Vacuum / Hg

VCM - Vehicle Control Module, the in-car computer that oversees engine management, transmission operation, anti-lock brakes, and other functions not directly related to emissions control

VIN - Vehicle Identification Number

VSS - Vehicle Speed Sensor

WOT - Wide Open Throttle

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