Diagnostic Trouble Codes - 1993
GMC
| 13 | Open Oxygen Sensor Circuit |
| 14 | Coolant Sensor Circuit Shorted |
| 15 | Coolant Sensor Circuit Open |
| 16 | Vehicle Speed Sensor Buffer Fault |
| 21 | Throttle Position Sensor (Signal Voltage High) |
| 22 | Throttle Position Sensor (Signal Voltage Low) |
| 24 | Vehicle Speed Sensor (VSS) Circuit |
| 25 | Manifold Air Temperature Sensor (MAT) Shorted |
| 28 | Pressure Switch Manifold (PSM) Fault |
| 32 | Exhaust Gas Recirculation System |
| 33 | Manifold Absolute Pressure Sensor (MAP) Voltage High) |
| 34 | Manifold Absolute Pressure Sensor (MAP) Voltage Low) |
| 35 | Idle Air Control (IAC) System |
| 37 | Brake Switch Stuck "On" |
| 38 | Brake Switch Stuck "Off" |
| 39 | Torque Converter Clutch (TCC) Stuck "Off" |
| 43 | Electronic Spark Control (ESC) Circuit |
| 44 | Oxygen Sensor Circuit Lean Exhaust Indicated |
| 45 | Oxygen Sensor Circuit Rich Exhaust Indicated |
| 51 | Faulty Mem-Cal or PROM Problem |
| 52 | Fuel CALPAK Missing |
| 53 | Over Voltage Error |
| 54 | Fuel Pump Circuit (Low Voltage) |
| 58 | Transmission Temperature Sensor Circuit (High Temp) |
| 59 | Transmission Temperature Sensor Circuit (Low Temp) |
| 66 | 3-2 Control Solenoid Circuit Fault |
| 67 | Torque Converter Clutch Solenoid Circuit Fault |
| 69 | TCC Stuck "On" |
| 72 | Vehicle Speed Sensor (VSS) Circuit |
| 73 | Pressure Control Solenoid Error |
| 75 | System Voltage Low |
| 79 | Transmission Fluid - Over Temperature |
| 81 | 2-3 Shift Solenoid Circuit Fault |
| 82 | 1-2 Shift Solenoid Circuit Fault |
To extract a trouble from the computer for diagnostic purposes, the Assembly Line Communication Link (ALDL) connector is used.
Ground terminals A and B with the ignition "ON" and engine not running. The system will enter the diagnostic mode. In this mode, the computer will display a 12, three consecutive times, by flashing the "CHECK ENGINE", "SERVICE ENGINE SOON" or "MALFUNCTION INDICATOR LAMP" or light. A 12 consists of one flash, a short pause, then two flashes in rapid succession.
After 12 is displayed, any stored trouble s will be displayed by flashing the "CHECK ENGINE", "SERVICE ENGINE SOON" or "MALFUNCTION INDICATOR LAMP" light. All s are displayed 3 times each then a 12 will repeat. In the diagnostic mode, the computer will also energize all computer controlled relays and solenoids.
ALDL Connector (Located Underdash)
The ALDL diagnostic connector is located in the passenger compartment.
