READING TROUBLE CODES
The control module stores component failure information under a related trouble code which can be recalled for diagnosis and repair. Read trouble codes by counting Malfunction Indicator Light (MIL) flashes or with diagnostic scan tester connected to the Data Link Connector (DLC). The tester is faster, and capable of reading information which would require testing individual control module and sensor/solenoid connector terminals with a digital voltmeter. Some models REQUIRE a scan tester to pull trouble codes. See SCAN TESTER DATA and SCAN TESTER USAGE .
Note. When using a scan tester, there is a time delay between serial data updates. For instantaneous response, a digital voltmeter must be used.
If scan tester is not available, MIL flashes can be read by grounding DLC terminal with ignition on and engine off. For example, FLASH, FLASH, pause, FLASH, longer pause, indicates Code 21. The first series of flashes are the first digit of trouble code. The second series of flashes are the second digit of trouble code. Trouble codes are displayed starting with the lowest code. Each code is displayed 3 times and will continue as long as DLC is grounded.
Note. Trouble codes will be recorded at various operating times. Some codes require sensor or switch operation for 5 seconds and others may require longer under certain conditions. Some codes may not set in a service bay operational mode.
| Code | Probable Cause |
|---|---|
| 12 | No Engine Speed Sensor Reference Pulse |
| CODE 13 | Open Oxygen Sensor Circuit |
| CODE 14 | Coolant Sensor Signal Voltage Low |
| CODE 15 | Coolant Sensor Signal Voltage High |
| CODE 16 | VSS Buffer Fault |
| CODE 21 | TPS Signal Voltage High |
| CODE 22 | TPS Signal Voltage Low |
| CODE 24 | Vehicle Speed Sensor - "C" & "K" Series |
| CODE 24 | VSS Transmission Output Signal - A/T |
| CODE 28 | Transmission Range Pressure Switch |
| CODE 32 | EGR Circuit Error Backpressure EGR With Sol - "G" Series |
| CODE 32 | EGR Circuit Error With Evrv Solenoid |
| CODE 32 | EGR Circuit Error - "P" Series With Linear EGR |
| CODE 32 | EGR Circuit Error - Series W/ Linear EGR |
| CODE 33 | MAP Sensor Signal Voltage High |
| CODE 34 | MAP Sensor Signal Voltage Low |
| CODE 35 | Idle Speed Error |
| CODE 36 | Idle Speed Actuator Fault - A/T |
| CODE 37 | TCC Brake Switch On |
| CODE 38 | TCC Brake Switch Off |
| CODE 39 | TCC Stuck Off - 4L80-E Transmission |
| CODE 42 | Ignition Control |
| CODE 43 | Knock Sensor Without Spark Module (Dual Sensors) |
| CODE 43 | Knock Sensor Without Spark Module (Single Sensor) |
| CODE 43 | Knock Sensor With Spark Control Module |
| CODE 44 | Lean Exhaust Indicated |
| CODE 45 | Rich Exhaust Indication |
| CODE 51 | PROM Error (Faulty Or Incorrect PROM) |
| CODE 52 | Faulty Calpak |
| CODE 52 | System Voltage High |
| CODE 53 | System Voltage High |
| CODE 54 | Fuel Pump Circuit |
| CODE 55 | ECM/PCM Error |
| CODE 58 | Transmission Fluid Temperature High |
| CODE 59 | Transmission Fluid Temperature Low |
| CODE 66 | 3-2 Control Solenoid Ckt Fault 4L60-E Transmission |
| CODE 67 | TCC Solenoid Circuit Check - 4L60-E Transmission |
| CODE 68 | Overdrive Ratio Error - 4L80-E Transmission |
| CODE 69 | Torque Converter Clutch Stuck On 4L60-E Transmission |
| CODE 69 | Torque Converter Clutch Stuck On 4L80-E Transmission |
| CODE 72 | VSS Circuit Loss Transmission Output Signal |
| CODE 73 | Pressure Control Solenoid (Current Error) |
| CODE 74 | Transmission Input Speed Error 4L80-E Transmission |
| CODE 75 | System Voltage Low |
| CODE 79 | Transmission Fluid Temperature High |
| CODE 81 | Transmission 2-3 Error |
| CODE 82 | Transmission 1-2 Error |
| CODE 83 | TCC Solenoid Circuit Fault (4L80E) |
| CODE 85 | Undefined Gear Ratio (4L80E) |
| CODE 86 | Low Gear Ratio ERROR (4L80E) |
| CODE 87 | High Gear Ratio ERROR (4L80E) |
TROUBLE CODE IDENTIFICATION
Note. On models not using "P" series codes, Code 12 should always exist when DLC test terminal is grounded with key on and engine off, but it may not be indicated by all makes of scan tester.