The little list of GMECM abbreviations, with explanations

AEAcceleration 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/FAir 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/ALCLAssembly 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
BLMBlock 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
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
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
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 Throttle

Maintained by Brian Koontz,

Thanks to Bowling & Grippo for their financial support of this site!