GM OBD-I Codes
1982-1995 Chevrolet, GMC, Buick, Cadillac, Pontiac and Oldsmobile. 74 codes. Paperclip codes. Jump terminals A and B on the ALDL connector, count the flashes.
Popular GM codes
- 13: Oxygen Sensor Circuit Open Or No Activity
- 14: Engine Coolant Temp Sensor Error High Temp Indicated
- 21: Throttle Position Sensor Error Signal High
- 24: Vehicle Speed Sensor Error
- 33: MAP Sensor Circuit Error Signal High
- 43: Knock Sensor Error
- 44: Oxygen Sensor Error Lean Condition Indicated
- 51: PROM Error
GM (74)
Jump to a system
Powertrain - Computer and Auxiliary Controls
- 12No Distributor Reference Pulse
- 16System Voltage Too Low
- 26Quad Driver Module A Error
- 27Quad Driver Module Second Gear Circuit Fault
- 29Quad Driver Module Fourth Gear Circuit Fault
- 46Pass Key Theft Deterrent System Error
- 47UART Serial Data Circuit Error
- 51PROM Error
- 52Fuel Calpak Incorrect Or Missing
- 53System Voltage Too High
- 55ECM Error
- 56Quad Driver Module QDM B Circuit Fault
- 61A/C System Performance Fault
- 66A/C Pressure Sensor Circuit Low Pressure Indicated
- 67A/C Pressure Sensor Circuit Fault
- 68A/C Clutch Relay Circuit Shorted To Ground
- 69A/C Clutch Relay Circuit Open Indicated
- 70A/C Pressure Sensor Circuit High Pressure Indicated
- 71A/C Evaporator Temp Sensor Circuit Low Temp Indicated
- 73A/C Evaporator Temp Sensor Circuit High Temp Indicated
- 85PROM Error
- 86ECM Analog To Digital Conversion Error
- 87EEPROM Error
- 98Invalid PCM Program
- 99Invalid PCM Program
- 18Crank Signal Circuit Fault
- 40Power Steering Pressure Switch Circuit Fault
Powertrain - Fuel/Air Metering
- 13Oxygen Sensor Circuit Open Or No Activity
- 14Engine Coolant Temp Sensor Error High Temp Indicated
- 15Engine Coolant Temp Sensor Error Low Temp Indicated
- 21Throttle Position Sensor Error Signal High
- 22Throttle Position Sensor Error Signal Low
- 23Intake Air Temp Sensor Error Low Temp Indicated
- 25Intake Air Temp Sensor Error High Temp Indicated
- 33MAP Sensor Circuit Error Signal High
- 34MAP Sensor Circuit Error Signal Low
- 35IAC Problem Or Idle Error
- 36MAF Sensor Error
- 44Oxygen Sensor Error Lean Condition Indicated
- 45Oxygen Sensor Error Rich Condition Indicated
- 54Fuel Pump Circuit Low Voltage
- 57Boost Control Solenoid Circuit Fault
- 63Right Bank O2 Sensor Circuit Open
- 64Right Bank O2 Sensor Lean Exhaust Indicated
- 65Right Bank O2 Sensor Rich Exhaust Indicated
- 20Fuel Pump Circuit Open
Powertrain - Ignition
- 17Camshaft Position Sensor Error
- 19Crankshaft Sensor Circuit Fault
- 41Ignition Control Error
- 42Ignition Bypass Circuit Error
- 43Knock Sensor Error
- 48Misfire Diagnosis
- 823X Crankshaft Position Sensor Circuit Error
Powertrain - Transmission
- 24Vehicle Speed Sensor Error
- 28Auto Transmission Range Pressure Switch Error
- 31Gear Position Switch Circuit Error
- 37TCC Brake Switch Circuit Error
- 38TCC Brake Switch Circuit Error
- 39Clutch Switch Circuit Error
- 58Trans Fluid Temp Sensor Circuit Low Voltage
- 59Trans Fluid Temp Sensor Circuit High Voltage
- 72Vehicle Speed Sensor Signal Circuit Error
- 79Transmission Fluid Over Temp
- 80Transmission Component Slipping
- 90Torque Converter Clutch Circuit Error
- 93Transmission Pressure Control Solenoid Circuit Error
- 96Transmission System Voltage Low
- 74Transmission Input Speed Error (4L80-E)
- 81Transmission 2-3 Shift Error
- 83TCC Solenoid Circuit Fault
Powertrain - Auxiliary Emissions Controls
How to read GM codes
- Find the ALDL connector under the dash, driver side.
- Jump terminals A and B with a paperclip. Key off first.
- Turn the key on, engine off. Count the check-engine flashes.
- Code 12 (one flash, pause, two flashes) means the system is ready. Fault codes follow, each flashed 3 times.
- Look up each code below. Remove the jumper before starting the engine.
New to this? How to Read GM OBD-I Codes with a Paperclip walks through the test and what the numbers mean.