Like any government instigated project, OBD-II quickly became a mouse's nest of acronyms, jargon, shorthand and code phrases that have meaning to the select few and sometimes seem to serve to keep the rest of us at bay.
AFC - Air Flow Control
ALDL - 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
CARB - California Air Resources Board
CFI - Central Fuel Injection (a.k.a. Throttle Body Fuel Injection TBI)
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- usually the main in-car computer controlling emissions and engine operation
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. Federal agency. Office of Mobile Sources is the branch concerned with auto emissions.
ESC - Electronic Spark Control
EST - Electronic Spark Timing
DPFE - Differential Pressure Feedback EGR sensor ( On Ford OBDII systems).
DTC - Diagnostic Trouble Code
FLI - Fuel Level Indicator
Fuel Trim - Engine computer function that keeps the air/fuel mixture as close to the ideal 14.7:1 stoichiometric ratio as possible
HC - Hydrocarbons
HEI - High Energy Ignition
HO2S - Heated 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
J1850PWM - (Pulse Width Modulated) SAE-established OBD II communication standard used by Ford domestic cars and light trucks. One of three hardware layers defined by OBD II
J1850VPW - (Variable Pulse Width Modulated) SAE-established OBD II communication standard used by GM cars and light trucks. 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.
NOx - Oxides of Nitrogen
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, the on-board computer that controls engine and drive train
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, professional organization that set the standards that EPA adopted for OBD and OBD II
Scan Tool - Computer based read-out equipment to display OBD II parameters
SES - Service Engine Soon dash light, now referred to as MIL
SFI - Sequential Fuel Injection
Stoichiometric ( Stoy'-kee-o-metric) 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
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