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 MANUALSPONTIAC1990FIREBIRD FORMULA, 5.0 F, AUTOMATIC, 4L60/MD8REPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCETESTING & DIAGNOSISENGINE CONTROLS - TESTS W/CODES - V8 PFI
1990 Pontiac Firebird Formula, 5.0 F, Automatic, 4L60/MD8
Engine Controls - Tests W/Codes - V8 PFI
1990 Pontiac Firebird Formula, 5.0 F, Automatic, 4L60/MD8SECTION Engine Controls - Tests W/Codes - V8 PFI
- Introduction
- Diagnostic Procedure
- Retrieving Codes (Non-Scan)
- Reading Trouble Codes
- Hard Or Intermittent Trouble Code Determination
- Clearing Trouble Codes
- ECM Location
- Diagnostic Materials
- Scan Tester Usage
- Code 13: Open Oxygen Sensor Circuit
- Code 14: Coolant Temp Sensor Signal Volt Low
- Code 15: Coolant Temp Sensor Signal Volt High
- Code 21: TPS Signal Volt High
- Code 22: TPS Signal Volt Low
- Code 23: Mat Sensor Signal Volt High
- Code 24: Vehicle Speed Sensor (5.0L & 5.7L F Body)
- Code 25: Mat Signal Voltage Low
- Code 32: EGR System Failure (5.0L & 5.7L F Body)
- Code 33: Map Sensor Signal Bolt High
- Code 34: Map Signal Voltage Low
- Code 41: Cylinder Select Error
- Code 42: Elect Spark Timing (5.0L & 5.7L W/HEI)
- Code 43: Elect Spark Control
- Code 44: Lean Exhaust Indication
- Code 45: Rich Exhaust Indication
- Code 46: Anti-Theft System (5.0L & 5.7L)
- Code 51: Mem-Cal Error
- Code 52: CALPAK/Mem-Cal Error
- Code 53: System OVERVOLTAGE
- Code 54: Fuel Pump Volt Low
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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.