1991 Chevrolet C1500 5.7L Engine Codes P22, P32, and P42: Diagnosis and Fixes
I own a 1991 Chevrolet C1500 with a 5.7L V8 engine. After performing a diagnostic check, I received trouble codes P22, P32, and P42. However, different automotive websites provide conflicting interpretations of these codes, making it difficult to determine the correct course of action. I'm seeking clear, reliable guidance on how to interpret and resolve each code. Any insights or step-by-step troubleshooting advice would be greatly appreciated.
Knowing the 8th character of the VIN is crucial for identifying the correct engine control system — in this case, if it's a Silverado with VIN character 'K', that helps pinpoint the system. Code P22: Throttle Position Sensor (TPS) — The TPS has three wires: gray (blue), black. Black serves as ground; gray provides a 5V reference. What voltage is present at the gray wire when the key is off (KOEO)? Typically, it should be around 4.8–5.0V. Blue wire is the return signal — what voltage do you read on this wire during KOEO? A reading of approximately 0.5–1.0V is expected. Code P32: EGR System — Check all vacuum lines connecting from the intake manifold to the electronic solenoid, and then from the solenoid to the EGR valve. Apply direct vacuum (bypassing the solenoid) to the EGR valve — does the engine stall? If yes, this suggests a damaged EGR diaphragm or faulty valve. Code P42: Exhaust Gas Recirculation Timing Bypass — First confirm that the timing connector for the EGR system is properly connected. Search online for the exact location of this connector in your 1991 C1500 model to ensure it's securely attached. How does your vehicle currently run? Have there been any recent modifications or repairs performed?