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 MANUALSBUICK1990REGAL CUSTOM, 3.8 L, 4T60/ME9REPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCETESTING & DIAGNOSISENGINE CONTROLS - TESTS W/CODES - 3.1L PFI
1990 Buick Regal Custom, 3.8 L, 4T60/ME9
Engine Controls - Tests W/Codes - 3.1L PFI
1990 Buick Regal Custom, 3.8 L, 4T60/ME9SECTION Engine Controls - Tests W/Codes - 3.1L PFI
- Introduction
- Self-Diagnostic System
- Diagnostic Tests
- Notes
- Code 13: Open Oxygen Sensor Circuit
- Code 14: Coolant Temp Sensor (Cts) Signal Voltage Low
- Code 15: Coolant Temp Sensor (Cts) Signal Voltage High
- Code 21: TPS Signal Voltage High
- Code 22: TPS Signal Voltage Low
- Code 23: Mat Sensor Signal Voltage High
- Code 24: Vehicle Speed Sensor
- Code 25: Mat Signal Voltage Low
- Code 31: WASTEGATE OVERBOOST (W Body Turbo)
- Code 32: EGR System Failure (Except W Body)
- Code 32: EGR System Failure (W Body Turbo)
- Code 32: EGR System Failure (W Body Non-Turbo)
- Code 33: Map Sensor Signal Voltage High
- Code 34: Map Signal Voltage Low
- Code 35: Idle Speed Error
- Code 41: Cylinder Select Error
- Code 42: Elect Spark Timing 3.1L W/Dis (Except F Body)
- Code 42: Elect Spark Timing (W/HEI)
- Code 43: Elect Spark Control
- Code 44: Lean Exhaust Indication
- Code 45: Rich Exhaust Indication
- Code 51: Mem-Cal Error
- Code 52: CALPAK/Mem-Cal Error
- Code 53: System OVERVOLTAGE
- Code 54: Fuel Pump Volt Low (Except J & W Body)
- Code 54: Fuel Pump Volt Low (J Body)
- Code 54: Fuel Pump Volt Low (W Body)
- Code 55: ECM Error (3.1L W Body Non-Turbo)
- Code 61: Degraded Oxygen Sensor (3.1L)
- Code 62: Gear Switch Error (A Body)
- Code 62: Gear Switch Error (3.1L J Body)
- Code 62: Gear Switch Error (3.1L L Body)
- Code 66: A/C Pressure Sensor (3.1L J Body)
- Summary
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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.