The little list of GMECM abbreviations, with explanations
| 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 Throttle