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 MANUALSPONTIAC1991FIREBIRD FORMULA, 5.0 F, STANDARD, M39REPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 15 (ENGINE CONTROLS - TESTS W/CODES - 3.1L PFI)
1991 Pontiac Firebird Formula, 5.0 F, Standard, M39
Section 15 (Engine Controls - Tests W/Codes - 3.1L PFI)
1991 Pontiac Firebird Formula, 5.0 F, Standard, M39SECTION Section 15 (Engine Controls - Tests W/Codes - 3.1L PFI)
WARNING: This page does not describe the selected car, but rather 10 other vehicles, including the 1992 Pontiac Sunbird, 1992 Pontiac Grand Prix, 1992 Pontiac Firebird, 1992 Oldsmobile Cutlass Supreme, and 1992 Chevrolet Lumina. However, it is still accessible from the selected car via links, so may be relevant.
- Introduction
- Model Identification
- Self-Diagnostic System
- Pcm/BCM Code Charts
- Notes
- Code 13, Open Oxygen (O2) Sensor Circuit
- Code 14, Coolant Temperature Sensor, Signal Voltage Low
- Code 15, Coolant Temperature Sensor, Signal Voltage High
- Code 21, Throttle Position Sensor, Signal Voltage High
- Code 22, Throttle Position Sensor, Signal Voltage Low
- Code 23, Mat Sensor Signal Voltage High
- Code 24, Vehicle Speed Sensor (VSS) "W" Body
- Code 25, Mat Sensor Signal Voltage Low
- Code 32, EGR System Error
- Code 33, Map Sensor, Signal Voltage High
- Code 34, Map Sensor, Signal Voltage Low
- Code 35, IAC Idle Speed Error, W/O Tech 1
- Code 35, IAC Idle Speed Error, Using Tech I
- Code 41, Cylinder Select Error
- Code 42, Est CKT Open Or Grounded
- Code 43, ESC Error, W/O ESC Module
- Code 44, Lean Exhaust Indication
- Code 45, Rich Exhaust Indication
- Code 46, Vehicle Anti-Theft System
- Code 51, Faulty Prom/Mem-Cal
- Code 52, Faulty Cal-PAK
- Code 53, System OVERVOLTAGE
- Code 54, Fuel Pump Voltage Low, "F", "J" & "L" Bodies
- Code 54, Fuel Pump Voltage Low, "W" Body
- Code 55, ECM Error
- Code 61, Degraded Oxygen (O2) Sensor
- Code 62, Gear Switch Error, "J" & "L" Bodies
- Code 66, A/C Pressure Sensor, "J", "L" & "W" Bodies
- 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.