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.
SYS.OK|MANUAL.DB● LIVE
HOMESERVICE MANUALSPONTIAC1991FIREBIRD FORMULA, 5.0 F, STANDARD, M39REPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 18 (ENGINE CONTROLS - TESTS W/CODES - 5.7L PFI)
1991 Pontiac Firebird Formula, 5.0 F, Standard, M39
Section 18 (Engine Controls - Tests W/Codes - 5.7L PFI)
1991 Pontiac Firebird Formula, 5.0 F, Standard, M39SECTION Section 18 (Engine Controls - Tests W/Codes - 5.7L PFI)
WARNING: This page is about a different car, the 1992 Pontiac Firebird, 1992 Chevrolet Corvette, and 1992 Chevrolet Camaro. 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 16, OPTI-Spark IGN. SYS, Low Resolution Pulse "Y" Body
- 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)
- Code 25, Mat Sensor Signal Voltage Low
- Code 26, Quad-Driver No. 1, "Y" Body
- Code 27, Quad-Driver No. 2, "Y" Body
- Code 28, Quad-Driver No. 3, "Y" Body
- 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 36, OPTI-Spark IGN. SYS, High Resolution Pulse, "Y" Body
- Code 41, OPTI-Spark IGN. SYS, Open/Shorted Est CKT, "Y" Body
- Code 42, Est CKT Open Or Grounded, "F" Body
- Code 42, OPTI-Spark IGN. System, Grounded Est CKT, "Y" Body
- Code 43, ESC Error, W/O ESC Module
- Code 44, Lean Exhaust Indication
- Code 45, Rich Exhaust Indication
- Code 46, Vehicle Anti-Theft System, "F" Body
- Code 51, Faulty Prom/Mem-Cal
- Code 52, Faulty Cal-PAK
- Code 52, Low Engine Oil Temperature, "Y" Body
- Code 53, System OVERVOLTAGE, "Y" Body
- Code 54, Fuel Pump Voltage Low, "F" Body
- Code 55, Fuel Lean Monitor, "Y" Body (1 Of 3)
- Code 55, Fuel Lean Monitor, "Y" Body (2 Of 3)
- Code 55, Fuel Lean Monitor, "Y" Body (3 Of 3)
- Code 55, ECM Error, "F" Body
- Code 62, High Engine Oil Temp, "Y" Body
- Code 63, Right Oxygen (O2) Sensor Open, "Y" Body
- Code 64, Right Oxygen (O2) Sensor Lean, "Y" Body
- Code 65, Right Oxygen (O2) Sens Rich, "Y" Body
- Code 66, A/C Pressure Sensor, "Y" Body
- Code 67, A/C Pressure Sensor, "Y" Body
- Code 68, A/C Relay CKT, Shorted To Voltage, "Y" Body
- Code 69, A/C Relay CKT Open, Or Shorted To Ground, "Y" Body
- Code 72, Gear Selector Switch, "Y" Body
- Summary
RENDER: 1.0x
NO RELATED
Recommended Tools & Savings
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Affiliate disclosure: We may earn a commission at no extra cost to you.
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.