Codes for GM 1982 & Newer
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Number 
Description
12 No reference pulses to Electronic Control Module (ECM)
13 Oxygen (O2) 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             CAM diagnostic
OR             Governor Malfunction
OR             Wastegate overboost
OR             Wastegate Eletrical Signal - open or shorted to ground 
32 Barometric Pressure (BARO) Sensor circuit failure
OR             Exhaust Gas Recirculation (EGR) valve diagnostic switch - closed during engine startup or open when EGR flow requested by ECM
OR             EGR / EVRV (Electronic Vacuum Regulator Valve) 
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 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 (IAC) 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 failure 
39 Torque Converter Clutch (TCC) circuit 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 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 (O2) Sensor voltage stays low after on or two minutes of engine run 
45 Rich exhaust indication - Oxygen (O2) Sensor voltage stays high after one minute of engine run 
46 Vehicle Anti-Theft Sytem (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-OnlyMemory (PROM) 
OR             Checksum errors
52 Electronic Control Module (ECM) computer circuit problems - fuel calpac missing, analog todigital converter (A/D) error 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
Number 
Description
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 Corrosivity / Add Collant 
OR             Port Throttle System Vacuum Sensor problems
58 Vehicle Anti-Theft System (VATS) problem
61 Oxygen (O2) Sensor degraded 
OR             Port Throttle System error 
OR             Cruise control problems - vent solenoid circuit
62 Gear switch imput 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 (O2) Sensor failure
64 Manifold Absolute Pressure (MAP) Sensor - signal voltage is low 
OR             Medium EGR failure
OR             Right Oxygen (O2) Sensor - lean condition indicated
65 Large EGR failure 
OR             Injector Peak / Hold Diagnostic
OR             Right Oxygen (O2) 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 occured 

 

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