Equus 3123 - GM Code Reader (1982 - 1995) - Manual (Page 19)

Retrieving ECM Codes
GM 2-10
CODE SERVICE CODE DEFINITION
42 Electronic spark timing (EST) circuit - open or shorted
Direct ignition system (DIS) fault - bypass circuit open
or shorted to ground during engine run
Fuel cutoff relay circuit - open or shorted to ground
43 Electronic spark timing (EST) circuit - low voltage
detected
Electronic spark control (ESC) - circuit problems
44 Lean exhaust indicated (Left side on dual oxygen models)
45 Rich exhaust indicated (Left side on dual oxygen
models)
46 Vehicle anti-theft system (VATS) failure
Power steering pressure switch failure
47 Circuit or component problem in ECM/PCM (communi-
cation error)
Knock sensor module error (inside computer)
48 Misfire symptom
Mass air flow (MAF) sensor - circuit error
49 RPM is high at idle (possible vacuum leak)
50 System voltage is low
51 Computer problem; faulty, wrong or incorrectly installed
PROM circuit; or ECM/PCM failure
52 Calibration Package Chip or ECM fault or oil tem-
perature sensor fault/low engine temperature
(Corvette); faulty or missing PROM/Calibration Package
Chip; ECM problem
System voltage high for a long period of time
53 System voltage too high (over 17.7 volts to ECM) or
EGR system fault or alternator voltage not normal or
Vehicle Anti-Theft System fault
54 Fuel pump circuit fault or Mixture Control (M/C)
solenoid fault or Electronic Control Module (ECM)
fault/EGR solenoid #2 failure (3.8L VIN1)
Fuel pump relay
55 Electronic Control Module (ECM) fault or oxygen sensor
circuit fault or EGR solenoid #3 failure (3.8L VIN1) or
fuel lean monitor (Corvette)