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GM CODES
12 No reference pulses to Electronic Control Module (ECM).
13 Oxygen (02) Sensor - signal stays low ("lean") during warm engine cruise.
14 Coolant Temperature Sensor (CTS) - signal voltage is low.
15 Coolant Temperature Sensor (CTS) - signal voltage is high.
16 High battery voltage or, Direct Ignition System (DIS) fault - line open or shorted to ground.
17 RPM signal problem.
21 Throttle Position Sensor TPS - signal voltage is high during engine idle or deceleration.
22 Throttle Position Sensor TPS - signal voltage is low during engine idle or, Fuel cutoff relay circuit - open or shorted to ground.
23 Manifold Air Temperature -(MAT) Sensor - signal voltage is low or, Throttle Position Sensor TPS error.
24 Vehicle Speed Sensor (VSS) - signal is constant (no pulsing) during engine deceleration.
25 Manifold Air Temperature (MAT) Sensor - signal voltage is low or, Vacuum Switching Valve Circuit - open or shorted to ground or, ATS sensor - signal voltage is high.
26 Quad driver module.
27 2nd gear switch
28 3rd gear switch.
29 4th gear switch.
31 Manifold Absolute Pressure (MAP) Sensor - signal voltage is low or, Fuel injector or, Park or Neutral switch or, CAM diagnostic or, Governor malfunction or, Wastegate overboost or, Wastegate Electrical Signal open or shorted to ground.
32 Barometric Pressure (BARO) Sensor circuit failure or, Exhaust Gas Recirculation (EGR) valve diagnostic switch - closed during engine start-up or open when EGR flow requested by ECM or, EGR/EVRV.
33 Mass Air Flow (MAF) Sensor - signal voltage or frequency is high during engine idle or, Manifold Absolute Pressure (MAP) Sensor - signal voltage is high during engine idle. (Note: Engine mis-fire or unstable idle may cause this code.)
34 Mass Air Flow (MAF) Sensor - signal voltage or frequency is, low during engine cruise, or, Manifold Absolute Pressure (MAP) Sensor - signal voltage is low during ignition on-
35 Idle Air Control OAC) system problem - can not set desired RPM.
36 Mass Air Flow (MAF) Sensor - burn-off circuit problem or, Transmission shift problem or, Direct Ignition System (DIS) fault - extra or missing pulses in Electronic Spark Timing (EST) signal -
38 Brake switch circuit fault.
39 Clutch, Torque Converter TCC circuits fault.
41 Cam Sensor (CAM) failure or, Cylinder Select Error or, Tach input Error - no reference pulses during engine run.
42 Electronic Spark Timing (EST) circuit - open or shorted to ground during engine run or, Direct Ignition System (DIS) fault - bypass circuit open or shorted to ground during engine run or, Fuel Cutoff Relay Circuit - open or shorted to ground.
43 Electronic Spark Timing (EST) circuit - low voltage detected.
44 Lean exhaust indication - Oxygen (0,) Sensor voltage stays tow after one or two minutes of engine run.
45 Rich exhaust indication - Oxygen (02) Sensor voltage stays high after one minute of engine run.
46 Vehicle Anti-Theft System (VATS) failure or, Power Steering Switch failure.
47 Electronic Control Module (ECM) computer circuit problems - Universal Asynchronous Receiver/ Transmitter (UART) link.
48 Misfire.
49 Vacuum leak.
51 Electronic Control Module (ECM) computer circuit problems - Programmable read-only Memory (PROM) or checksum errors.
52 Electronic Control M6dule (ECM) computer circuit problems - fuel calpac missing, analog to digital converter (A/D) error or quad driver module (QDM) fault or, Oil Temperature Sensor - signal voltage is low.
53 Over voltage condition or, Exhaust Gas Recirculation (EGR) or, Voltage reference error or, Vehicle Anti-Theft System (VATS) problems.
54 Low fuel pump voltage or, Fuel pump relay or, Quad Driver Module (QDM) output failure.
55 Electronic Control Module (ECM) computer circuit problems - ECM failure, Serial Bus error, SAD error or, Fuel lean malfunction.
56 Corrosivfty/add coolant or, Port Throttle System Vacuum Sensor problems.
S8 Vehicle Anti-Theft System (VATS) problem.
61 Oxygen (0,) Sensor degraded or, Port Throttle System error or, Cruise control problems - vent solenoid circuit.
62 Gear switch input diagnostics or, Oil Temperature Sensor - signal voltage is high or, Cruise Control Problems - vacuum solenoid circuit.
63 Manifold Absolute Pressure (MAP) Sensor - signal voltage is high or, Small EGR failure or, Right Oxygen (02) Sensor failure.
64 Manifold Absolute Pressure (MAP)-Sensor --. signal voltage is low or, Medium EGR failure or, Right Oxygen (02) Sensor - lean condition indicated.
6S Large EGR failure or, Injector Peak/hold Diagnostic or, Right Oxygen (02) Sensor - rich condition indicated or, Cruise Control Position Sensor problem.
66 Electronic Control Module. (ECM) computer circuit problem - internal reset occurred.
67 Cruise Control - switch circuit problems.
68 Cruise control - system circuit problems.
69 Air Conditioner Pressure Switch - circuit problems.
88 Electronic Control Module (ECM) computer circuit problem - internal reset occurred.
If more than one definition is listed, consult your vehicle service manual to get the specific meaning for your vehicle.(home)