ECM TROUBLE CODE DEFINITIONS
| Code No. | Circuit Affected |
|---|---|
| 12 (1) | No RPM reference pulse |
| 13 | Open oxygen sensor circuit |
| 14 | Coolant sensor circuit shorted |
| 15 | Coolant sensor circuit open |
| 21 | TPS signal voltage high |
| 22 | TPS signal voltage low |
| 23 | MAT voltage high |
| 23 | M/C solenoid voltage low |
| 24 | VSS circuit |
| 25 | MAT sensor signal voltage low |
| 31 | Purge sol. voltage high (carb.) |
| 32 | EGR vacuum control signal |
| 32 | BARO voltage low (carb.) |
| 33 | MAP sensor voltage high |
| 33 | MAF sensor frequency high (PFI) |
| 34 | MAP sensor voltage low |
| 34 | VAC sensor circuit |
| 34 | MAF sensor frequency low (PFI) |
| 35 | IAC (EFI) or ISC (carb.) speed error |
| 36 | MAF sensor burnoff |
| 41 | No distributor reference (HEI) |
| 41 | C(3)I ignition - cam sensor loss |
| 41 | Cylinder select error (MEM-CAL) |
| 42 | EST circuit open or grounded |
| 43 | ESC retard signal too low |
| 44 | Lean oxygen sensor value |
| 45 | Rich oxygen sensor value |
| 51 | Faulty PROM, MEM-CAL or ECM |
| 52 | Faulty/missing CALPAC or MEM-CAL |
| 53 | Faulty alternator, voltage high |
| 54 | Fuel pump voltage low |
| 55 | Faulty ECM |
| (1) Code "12" should be displayed only when no reference pulses are received by ECM (engine not running). | |
| (1) | Code "12" should be displayed only when no reference pulses are received by ECM (engine not running). |
ECM TROUBLE CODE DEFINITION
Note. Trouble code charts should only be used if "SERVICE ENGINE SOON" light is illuminated (indicating a current problem exists). Exceptions are Code 13, 15, 24, 44 and 45 charts, which may be used to help diagnose intermittent codes.
Note. Any time Codes 51, 52, 54 or 55 are displayed with another code, start with "50-series" code first, then proceed to low profile numbered code.