| Abbreviation | Explanation |
| AE | Acceleration enrichment. Similar to the accelerator pump on a carb. Additional fuel is injected for rapid throttle openings, or rapid decreases in MAP. Compensates for sensor lag, and also for fuel condensing out of the air when MAP decreases. Less AE is used on dry manifold (port injected) applications. |
| A/F | Air to fuel ratio. Expressed in mass. 14.7 parts air to 1 part fuel is "stoich", the point at which, ideally, all of the fuel and all of the oxygen are consumed, with none left over. Less than 14.7 is rich, greater than 14.7 is lean |
| ALDL/ALCL | Assembly line diagnostic/communication link. This is the serial line over which scan tools communicate with the ECM/PCM. Trouble codes are available, as well as various engine parameters. There are 2 bit rates, 160 bps and 8192. The ALDL connector is typically found under the dash, on the driver's side. This is the point where terminals A and B may be shorted to view trouble codes on the check engine light |
| BLM | Block learn multiplier. Part of the self tuning capability of the ECM. An ECM typically has a table of BLM values, indexed by MAP and RPM. When the engine is in closed loop mode, the O2 sensor is monitored and fuel is either added or subtracted to maintain 14.7:1. Over time these changes accumulate in the BLM table. |
BLM Block Learn Multiplier bpw base pulse width BTU British Thermal Units C Celsius C/L Closed Loop C3 GM ECM using Motorola 68xx-like processor (1+ MHz CPU) CCP Controlled Canister Purge CEL Check engine light CID Cubic Inch Displacement CKP crankshaft position sensor CMP camshaft position sensor CP Canister Purge CPU Central Processor Unit (the brains in the ecm) CTS Coolant Temp Sensor DB Decibels DC Duty Cycle On time, compared to total event time expressed as a percent DC Direct Current DE Decel Enleanment DFCO Decleration Fuel Cut Off DIS Distributorless Ignition System DVM Digital Multi Meter ECM Engine Control Module ECT engine coolant temp ECU Engine Control Unit EFI Electronic Fuel Injection EGR Exhaust Gas Recirculation EGT Exhaust Gas Temp EPROM Erasable Programable Read Only Memory ESC Electronic Spark Control (Knock Control) EST Electronic Spark Timing F Fahrenheit FED Federal (emissions package) GPS Grams per sec hego heated exhaust gas oxygen HEI High Energy Ignition HO2S heated o2 sensor I/O Input/Output IAC Idle Air Control IAT Intake Air Temp IC Integrated Circuit ICE Internal Combustion engine IGN Ignition Injector On Time Time in milliseconds that an injector is on. INT Integrator IPW Injector Pulse Width IS Idle Speed ISC Idle Speed Control kapwr keep alive power kg Kilogram Kilohertz (1,000s cycles / sec) kPa Kilopascals (Pressure) KS Knock Sensor L Liter (about 60 cubic inches) LCD Liquid Crystal Display MAF Mass Air Flow MAP Manifold Absolute Pressure MAT Manifold Air Temp MDP Manifold differential Pressure MEMCAL Memory Calibration Unit MFI Multi-port Injection MIL malfunction indicator lamp MT Manual Transmission NC Normally Closed NEU Neutral NO Normally Open NPTC National Pipe thread Course NTPF National Pipe Thread Fine O2 Sensor for detecting rich lean exhaust mixtures, GM so far uses this type, and it has a high slew rate and therefore is more of a switch OBD2 on board diagnostics, newer vehicle electronics, less friendly OL Open Loop OTS Oil Temp Sensor P/N park neutral switch P+H one way of firing an injector High initial voltage to open then lower to keep it open P4 GM ECM using early Motorola 68HCxx-like processor (2+ MHz CPU) PCM Powertrain Control Module (engine and trans control) PE Power Enrichment Port, MPFI, Multi Port, each cyl has it's own injector close to the intake valve PS Power steering PSI Pounds per square inch PSIA PSI absolute PSIG PSI Gauge PW Pulse Width PWM Pulse Width Modulation QT Quart R-12 Refrigerant RAM Random Access Memory RAP Retained Accessory Power RFI Radio Frequency Interference ROM Read Only Memory RR Right Rear RTV Room Temperature Vulcanizing RWD Rear wheel drive SEFI Sequential Electronic Fuel Injection SES Service Engine Soon (Light) SI Saturated Injector *constant* voltage current SynchPulse Fuel PW with delivery tied to timing of ref pulses TAC Thermostatic Air Cleaner TB Throttle Body TBI Injection system where the injectors are mounted above the butterflies TCC Torque Converter Clutch TCM Transmission Control Module TDC Top Dead Center TFT trans fluid temp TH Turbo-Hydramatic TPI Tuned Port Injection TPS Throttle Position Sensor TRC Throttle Return Control TTS Trans Temp Sensor TV Throttle Valve TVS Thermal Vacuum Switch VATS Vehicle Anti Theft System VE Volumetric Efficiency VSS Vehicle Speed Sensor WBO2 this sensor differs from the O2 in so far that it is designed for a *linear* output WG WasteGate WOT Wide Open ThrottleMaintained by Brian Koontz, brian@diy-efi.org
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