OBD-II Acronyms and JargonPosted by Alex (Im) E. on 31 January 2013 09:15 PMLIST 1AFC - Air Flow ControlALDL - 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 signalsCAN - Controller Area NetworkCARB - California Air Resources BoardCFI - Central Fuel Injection (a.k.a. Throttle Body Fuel Injection TBI)CFI - Continuous Fuel InjectionCO - Carbon MonoxideDLC - Data Link ConnectorDriving Cycle - A specific sequence of start-up, warm-up and driving tasks that tests all OBD II functionsDTC - Diagnostic Trouble CodeECM - Engine Control Module- usually the main in-car computer controlling emissions and engine operationECT - Engine Coolant TemperatureECU - Engine Control UnitEEC - Electronic Engine ControlEEPROM or E2PROM - Electrically Erasable Programmable Read Only MemoryEFI - Electronic Fuel InjectionEGR - Exhaust Gas RecirculationEMR - Electronic Module RetardEPA - Environmental Protection Agency. Federal agency. Office of Mobile Sources is the branch concerned with auto emissions.ESC - Electronic Spark ControlEST - Electronic Spark TimingDPFE - Differential Pressure Feedback EGR sensor ( On Ford OBDII systems).DTC - Diagnostic Trouble CodeFLI - Fuel Level IndicatorFuel Trim - Engine computer function that keeps the air/fuel mixture as close to the ideal 14.7:1 stoichiometric ratio as possibleHC - HydrocarbonsHEI - High Energy IgnitionHO2S - Heated Oxygen SensorIAT - Intake Air TemperatureISO 9141 - International Standards Organization OBDII communication mode, used by Chrysler and most foreign cars. One of three hardware layers defined by OBD IIJ1850PWM - (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 IIJ1850VPW - (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 IIJ1962 - SAE-established standard for the connector plug layout used for all OBD II scan toolsJ1978 - SAE-established standard for OBD II scan toolsJ1979 - SAE-established standard for diagnostic test modesJ2012 - SAE-established standard accepted by EPA as the standard test report language for emission testsMAF - Mass Air FlowMAP - Manifold Absolute PressureMAT - Manifold Air TemperatureMFG - ManufacturerMIL - Malfunction Indicator Light. The "Check Engine Light" on your dash.NOx - Oxides of NitrogenO2 - OxygenOBD - On-Board DiagnosticsOBDII or OBD II - Updated On-Board Diagnostics standard effective in cars sold in the US after 1-1-96Parameters - Readings on scan tools representing functions measured by OBD II and proprietary readingsPCM - Powertrain Control Module, the on-board computer that controls engine and drive trainPCV - Positive Crankcase VentilationPID - Parameter IDProprietary 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 CodeRPM - Revolutions Per MinuteSAE - Society of Automotive Engineers, professional organization that set the standards that EPA adopted for OBD and OBD IIScan Tool - Computer based read-out equipment to display OBD II parametersSES - Service Engine Soon dash light, now referred to as MILSFI - Sequential Fuel InjectionStoichiometric ( Stoy'-kee-o-metric) Ratio - Theoretical perfect combustion ratio of 1 part gas to 14.7 parts airTBI - Throttle Body InjectionTPI - Tuned Port InjectionTPS - Throttle Position SensorVAC - VacuumVCM - Vehicle Control Module, the in-car computer that oversees engine management, transmission operation, anti-lock brakes, and other functions not directly related to emissions controlVIN - Vehicle Identification NumberVSS - Vehicle Speed SensorWOT - Wide Open ThrottleLIST 2A/C: air conditioningAC: air cleanerAIR: secondary air injectionA/T: automatic transmission or transaxleB+: battery positive voltageBARO: barometric pressureBCM: body control moduleCAC: charge air coolerCFI: continuous fuel injectionCL: closed loopCKP: crankshaft position sensorCKP REF: crankshaft referenceCMP: camshaft position sensorCMP REF: camshaft referenceCO: carbon monoxideCO2: carbon dioxideCPP: clutch pedal positionCTOX: continuous trap oxidizerCTP: closed throttle positionDEPS: digital engine position sensorDFCO: decel fuel cut-off modeDFI: direct fuel injectionDIC: driver information centerDLC: data link connectorDTC: diagnostic trouble codeDTM: diagnostic test modeEBCM: electronic brake control moduleEBTCM: electronic brake traction control moduleEC: engine controlECM: engine control moduleECL: engine coolant levelECT: engine coolant temperatureEEPROM: elecrically erasable programmable read only memoryEFE: early fuel evaporationEGR: exhaust gas recirculationEGRT: EGR temperatureEI: electronic ignitionEPROM: erasable programmable read only memoryEVAP: evaporative emission systemFC: fan control FF: flexible fuelFP: fuel pumpFT: fuel trimFTP: federal test procedureGCM: governor control moduleGEN: generator (alternator)GND: groundH20: waterHO2S: heated oxygen sensorHO2S1: upstream heated oxygen sensorHO2S2: up or downstream heated oxygen sensorHO2S3: downstream heated oxygen sensorHC: hydocarbonHVAC: heating ventilation and air conditioning systemIA: intake airIAC: idle air controlIAT: intake air temperatureIC: ignition control circuitICM: ignition control moduleIFS: inertia fuel shutoffI/M: inspection/maintenanceI/M 240: inspection/maintenance 240 emissions testIPC: instrument panel clusterISC: idle speed controlKOEC: key on, engine crankingKOEO: key on, engine offKOER: key on, engine runningKS: knock sensorKSM: knock sensor moduleLEV: low emission vehicleLT: long term fuel trimMAF: mass airflow sensorMAP: manifold absolute pressure sensorMC: mixture controlMDP: manifold differential pressureMFI: multiport fuel injectionMIL: malfunction indicator lampMPH: miles per hourNOX: oxides of nitrogenO2S: oxygen sensorOBD: onboard diagnosticsOBD I: onboard diagnostics generation oneOBD II: onboard diagnostics, second generationOC: oxidation catalystODM: output device monitorOL: open loopOSC: oxygen sensor storagePAIR: pulsed secondary air injectionPCM: powertrain control modulePCV: positive crankcase ventilationPNP: park/neutral switchPROM: program read only memoryPSA: pressure switch assemblyPSP: power steering pressureRAM: random access memoryRM: relay moduleROM: read only memoryRPM: revolutions per minute (engine speed)SC: supechargerSCB: supercharger bypass (wastegate)SDM: sensing diagnostic modeSFI: sequential fuel injectionSRI: service reminder indicatorSRT: system readiness testST: short term fuel trimTB: throttle bodyTBI: throttle body injectionTC: turbochargerTCC: torque converter clutchTCM: transmission or transaxle control moduleTFP: throttle fluid pressureTP: throttle positionTPS: throttle position sensorTVV: thermal vacuum valveTWC: three way catalystTWC+OC: three way + oxidation catalytic converterULEV: ultra low emission vehicleVAF: volume airflowVCM: vehicle control moduleVR: voltage regulatorVS: vehicle sensorVSS: vehicle speed sensorWU-TWC: warm up three way catalytic converterWOT: wide open throttleZEV: zero emission vehicleTECHNICAL TERMSBaud Rate: The speed at which bits of computer data are transmitted through the serial data stream or on the controller area network (CAN) bus.Bus: Another name for the basic circuit that carries data between all the modules in a vehicle. Also refered to as the Controller Area Network (CAN) bus.CAN: Controller Area Network, the bus circuit over which all the modules in the vehicle communicate with each other. Communication faults over the bus can cause unpredictable driveability problems and will set special fault codes.Closed Loop: An operating mode of the fuel feedback control system where the powertrain control module uses the rich/lean signal from the oxygen sensor to control the fuel mixture. Closed loop usually does not occur until the oxygen sensor is hot to produce a signal, and the engine has reached a certain temperature. The sooner the engine goes into closed loop operation, the lower are its emissions. A faulty coolant sensor, oxygen sensor or thermostat can prevent the engine from going into closed loop. This usually causes the engine to run rich and pollute.Code Reader: A type of diagnostic tool that plugs into the OBD II diagnostic connector and displays fault codes. A code reader can also be used to clear codes, and some will show OBD II readiness flags, but most are not capable of reading sensor data or other system information.Downstream O2 sensor: The oxygen sensor located behind (downstream) of the catalytic converter. This sensor is used primarily to monitor the operating efficiency of the catalyst, but may also be used for long term fuel trim.Drive Cycle: When the engine is started, allowed to reach operating temperature and then shut down. It may or may not involve actually driving the vehicle.Enable Criteria: The set of conditions needed for a diagnostic test or OBD II monitor to run.Fuel trim: This is the fine-tuning of the air/fuel mixture. There is both short term fuel trim and long term fuel trim. Short term compensates for changing operating conditions. Long term compensates for engine wear and other variables.Loaded Mode Testing: A type of emissions testing that places a load on the vehicle to simulate driving conditions. This is done on a dynamometer while the vehicle is driven at various speeds. Loaded mode testing is used in both I/M 240 and ASM emissions testing.Misfire Detection: An OBD II monitor that detects misfire in one or more cylinders. Misfire may be caused by ignition, fuel or compression problems. If misfires exceed a certain rate, it sets a misfire code which corresponds to the cylinder(s) involved. If the misfire jumps around from cylinder to cylinder, OBD II sets a "random misfire" code (P0300) which maybe the result of a vacuum leak, EGR leak or low fuel pressure.Monitor: A self-diagnostic check run by OBD II on a system or component.Open Loop: An operating mode of the fuel feedback control system where the fuel mixture is fixed (unchanging) and is predetermined by the computer. The engine remains in open loop after it is first started and until it reaches a certain temeprature and the oxygen sensor is hot enough to produce a good signal.Readiness Code or Flag: An indication that a particular OBD II monitor has run or has been completed. Emission test requirements requires that all by one or two readiness monitors be completed before a vehicle can pass an OBD II emissions test (NOTE: this requirement varies by model year and state).Scan Tool: A type of diagnostic tool that plugs into the OBD II diagnostic conenctor to access system information including fault codes, history codes, sensor data and other information. Professional grade scan tools are also "bidirectional" and can be used to perform special tests. Some can also be used to reprogram the vehicle computer.Trip: Driving the vehicle long enough and under the right conditions so that all the OBD II system and component monitors have run at least once.Upstream O2 sensor: The oxygen sensor located in the exhaust manifold and ahead (upstream) of the catalytic converter. This sensor is used by the fuel feedback control system to monitor the relative richness or leanness of the air/fuel mixture for emissions, fuel economy and performance.Warm-up Cycle: Starting a cold engine and allowing it to warm up at least 40 degrees F (22 degrees C) and reach a minimum of 160 degrees F (70 degrees C).