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 PERFORMANCESYSTEMENGINE CONTROLS - TESTS W/CODES - 3.8L VIN [L]
1990 Buick Regal Custom, 3.8 L, 4T60/ME9
Engine Controls - Tests W/Codes - 3.8L VIN [L]
1990 Buick Regal Custom, 3.8 L, 4T60/ME9SECTION Engine Controls - Tests W/Codes - 3.8L VIN [L]
- Introduction
- Self-Diagnostic System
- Diagnostic Code Charts: 13 To 66
- Notes
- Code 13 - Oxygen Sensor Circuit (Open Circuit)
- Code 14 - Coolant Temperature Sensor Circuit (High Temp)
- Code 15 - Coolant Temperature Sensor Circuit (Low Temp)
- Code 16 - Battery Voltage Too High Or Too Low
- Code 17 - Rpm Signal Problem (Spark Reference Circuit)
- Code 21 - Throttle Position Sensor Circuit (Voltage High)
- Code 22 - Throttle Position Sensor Circuit (Voltage Low)
- Code 23 - Air Temperature (Mat) Sensor CKT (Temp Low)
- Code 24 - Vehicle Speed Sensor (VSS) Circuit
- Code 25 - Air Temperature (Mat) Sensor CKT (Temp High)
- Code 26 - Quad-Driver (QDM) Circuit
- Code 27, 28 Or 29 - Gear Switch Circuits
- Code 31 - Park/Neutral (P/N) Switch Circuit
- Code 34 - Mass Airflow (MAF) Sensor Circuit
- Code 38 - Brake Switch Circuit
- Code 39 - Torque Converter Clutch (TCC) Circuit
- Code 41 - Cam Sensor Circuit
- Code 42 - Electronic Spark Timing (Est) Circuit
- Code 43 - Electronic Spark Control (ESC) Circuit
- Code 44 - Oxygen Sensor Circuit (Lean Exhaust Indicated)
- Code 45 - Oxygen Sensor Circuit (Rich Exhaust Indicated)
- Code 51, Mem-Cal Error
- Code 66 - Low A/C Refrigerant Charge
- 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.