Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
1987 Pontiac Fiero Base, Standard, MG3FACTORY OEM SERVICE PROCEDURE
ECM Trouble Code Definitions
ECM TROUBLE CODE DEFINITION
| Code No. | Circuit Affected |
|---|---|
| 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 |
| 24 | VSS circuit |
| 25 | MAT sensor signal voltage low |
| 32 | EGR vacuum control signal |
| 33 | MAP sensor voltage high |
| 34 | MAP sensor voltage low |
| 35 | IAC (EFI) speed error |
| 42 | EST circuit open or grounded |
| 44 | Lean oxygen sensor value |
| 45 | Rich oxygen sensor value |
| 52 | Faulty/missing CALPAC or MEM-CAL |
| 53 | Faulty alternator, voltage high |
| 55 | Faulty ECM |
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.
Factory Service Tools
Use the Manual With the Right Hardware
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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