General Motors Diagnostic Codes

The are the General Motors Diagnostic Trouble codes.
They are for all General Motors Vehicles except Front Wheel Drive Cadillac Vehicles.
This list is for reference only and does not mean a specific part is defective, only that the system specified has malfunctioned.
For information on reading codes click here.

CODEMEANING
12No engine RPM reference pulses--System Normal
13Oxygen Sensor (02S) circuit open--left side on 2 sensor system
14Engine Coolant Temperature (ECT) sensor-- possible circuit high or shorted circuit
15Engine Coolant Temperature (ECT) sensor-- possible circuit low or open circuit
16 Direct Ignition System (DIS), fault line circuit
  -or- Distributor ignition system (low resolution pulse)
  -or- Missing 2X reference circuit
  -or- OPTI-Spark ignition timing system (low resolution pulse)
  -or- System voltage out of range
17Camshaft Position Sensor (CPS) or spark reference circuit error
18Crank/Cam error
19Camshaft Position Sensor (CPS) circuit
21Throttle Position (TP) sensor circuit--signal out of range, probably high
22Throttle Position (TP) sensor circuit--signal voltage low
23Intake Air Temperature (IAT or MAT) sensor circuit--temperature out of range, low
  -or- Open or grounded M/C solenoid--Feedback carburetor system
24Vehicle Speed Sensor (VSS) circuit
25Intake Air Temperature (IAT or MAT) sensor circuit--temperature out of range, high
26Quad-Driver Module (QDM) #1 circuit
  -or- Transaxle gear switch circuit
27Quad-Driver Module (QDM) circuit
  -or- Transaxle gear switch, probably 2nd gear switch circuit
28Quad-Driver Module (QDM) #2 circuit
  -or- Transaxle gear switch, probably 3rd gear switch circuit
29Transaxle gear switch, probably 4th gear switch circuit
31Camshaft sensor circuit fault
  -or- Park/Neutral Position (PNP) switch circuit
  -or- Wastegate circuit signal
32Exhaust Gas recirculation (EGR) circuit fault
  -or- Barometric Pressure Sensor circuit low--Feedback Carburetor system
33Manifold Absolute Pressure (MAP) sensor--signal out of range, high
  -or- Mass Air Flow (MAF) sensor--signal voltage out of range, probably high
34Manifold Absolute Pressure (MAP) sensor--signal out of range, low
  -or- Mass Air Flow (MAF) sensor circuit (gm/sec low)
35Idle Air Control (IAC) or idle speed error
  -or- Idle speed Control (ISC) circuit--throttle switch shorted--Feedback Carburetor system
36Ignition system circuit error
  -or- Transaxle shift problem--4T60E Transaxle
38Brake input circuit fault--torque converter clutch signal
39Clutch input circuit fault--Torque converter clutch signal
41Cam sensor or cylinder select circuit fault--ignition control (IC) reference pulse system fault
  -or- Electronic Spark Timing (EST) circuit open or shorted
42Electronic Spark Timing (EST) circuit grounded
  -or- Ignition Control circuit grounded or faulty bypass line
43Knock Sensor (KS) or Electronic Spark Control (ESC) circuit fault
44Oxygen Sensor (O2S), left side on 2 sensor system--lean exhaust indicated
45Oxygen Sensor (O2S), left side on 2 sensor system--rich exhaust indicated
46Personal Automotive Security System (PASS-KEY II) circuit
  -or- Power Steering Pressure Switch (PSPS) circuit
47PCM-BCM data circuit
48Misfire diagnosis
51Calibration error, faulty MEM-CAL, ECM or EEPROM failure
52Engine oil temperature sensor circuit, low temperature indicated
  -or- Fuel Calpac missing
  -or- Over voltage condition
  -or- EGR Circuit fault
53Battery voltage error
  -or- EGR problem
  -or- Personal Automotive Security System (PASS-KEY II) circuit
54EGR #2 problem
  -or- Fuel pump circuit (low voltage)
  -or- Shorted mixture control solenoid circuit--Feedback Carburetor system
55A/D Converter error
  -or- PCM error or not grounded
  -or- EGR #3 problem
  -or- Fuel lean monitor
  -or- Grounded voltage reference, faulty oxygen sensor, full lean-- Feedback Carburetor system
56Quad-Driver Module (QDM) #2 circuit
  -or- Secondary air inlet valve actuator vacuum sensor circuit signal high--(5.7L VIN J)
57Boost control problem
58Vehicle Anti-theft System fuel enable circuit
61A/C system performance
  -or- Cruise vent solenoid circuit fault
  -or- Oxygen Sensor (O2S)--degraded signal
  -or- Secondary port throttle valve system fault--(5.7L VIN J)
  -or- Transaxle gear switch signal
62Cruise vacuum solenoid circuit fault
  -or- Engine oil temperature sensor, high temperature indicated
  -or- Transaxle gear switch signal circuit fault
63Oxygen Sensor (O2S), right side--circuit open
  -or- Cruise system problem (speed error)
  -or- Manifold Absolute Pressure (MAP sensor--circuit out of range
64Oxygen Sensor (O2S), right side--lean exhaust indicated
65Oxygen Sensor (O2S), right side--rich exhaust indicated
  -or- Cruise servo position circuit
  -or- Fuel injector circuit low current
66A/C pressure sensor circuit fault, probably low pressure
  -or- Engine power switch, voltage high or low or PCM fault (5.7L VIN J)
67A/C pressure sensor circuit, sensor or A/C clutch circuit failure
  -or- Cruise switch circuit fault
68A/C compressor relay (shorted circuit)
  -or- Cruise system fault
69A/C clutch circuit or head pressure high
70A/C refrigerant pressure sensor circuit (high pressure)
71A/C evaporator temperature sensor circuit (low temperature)
72Gear selector switch circuit
73A/C evaporator temperature sensor circuit (high temperature)
75Digital EGR #1 solenoid error
76Digital EGR #2 solenoid error
77Digital EGR #3 solenoid error
79Vehicle Speed Sensor (VSS) circuit signal high
80Vehicle Speed Sensor (VSS) circuit signal low
81Brake input circuit fault--Torque converter clutch signal
82Ignition Control (IC) 3X signal error
85PROM error
86Analog/Digital ECM error
87EEPROM error
99Power management