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.
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HOMESERVICE MANUALSBUICK1990SKYLARK BASE, 4D SEDAN, 125C/MD9REPAIR AND DIAGNOSISENGINE PERFORMANCESYSTEMENGINE CONTROLS - TESTS W/CODES - 2.5L TBIECM TROUBLE CODE DEFINITION TABLE
1990 Buick Skylark Base, 4D Sedan, 125C/MD9
ECM Trouble Code Definition Table
1990 Buick Skylark Base, 4D Sedan, 125C/MD9SECTION ECM Trouble Code Definition Table
ECM TROUBLE CODE DEFINITION
| Code No. | Circuit Affected | ||
|---|---|---|---|
| 12 (1) | No RPM reference pulse | ||
| 13 | Open oxygen sensor circuit | ||
| 14 | CTS signal voltage low | ||
| 15 | CTS signal voltage high | ||
| 16 | System voltage high | ||
| 21 | TPS signal voltage high | ||
| 22 | TPS signal voltage low | ||
| 23 | MAT sensor signal voltage high, M/C solenoid voltage low | ||
| 24 | VSS circuit | ||
| 25 | MAT sensor signal voltage low | ||
| 26 | Quad-Driver error | ||
| 27, 28 & 29 | Gear switch problem | ||
| 31 | Park/Neutral switch | ||
| 32 | EGR system error | ||
| 33 | MAP sensor signal voltage high | ||
| 34 | MAP sensor signal voltage low | ||
| 35 | IAC idle speed error | ||
| 38 | Brake switch | ||
| 39 | TCC | ||
| 41 | C(3)I ignition - cam sensor loss, Cylinder select error (MEM-CAL) | ||
| 42 | EST circuit open or grounded | ||
| 44 | Lean exhaust indicated | ||
| 45 | Rich exhaust indicated | ||
| 46 | Anti-theft fault, Power steering pressure switch | ||
| 48 | Misfire diagnosis | ||
| 51 | Faulty PROM, MEM-CAL or ECM | ||
| 52 | Faulty/missing CALPAC or MEM-CAL | ||
| 53 | Faulty alternator, voltage high, EGR system malfunction, Anti-theft circuit fault | ||
| 54 | Fuel pump voltage low | ||
| 55 | Faulty ECM | ||
| 61 | Degraded O2 sensor | ||
| 62 | Gear switch error | ||
| 63 | EGR flow error | ||
| 64 | EGR flow error | ||
| 65 | EGR flow error, Fuel injector current low | ||
| 66 | A/C pressure sensor voltage, out of specification | ||
|
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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. Anytime Codes 51, 52, 54 or 55 are displayed with another code, start with 50-series code first, then proceed to low profile numbered codes.
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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.