P0102 and P0340 Troubleshooting - 1997 Chevrolet K1500 5.7L V8
I own a 1997 Chevrolet K1500 pickup with a 5.7L V8 engine, and I'm currently experiencing two diagnostic trouble codes: P0102 (Mass Airflow Sensor Range/Performance Problem) and P0340 (Camshaft Position Sensor Circuit Malfunction). After replacing both the Mass Airflow (MAF) sensor and the Camshaft Position (CMP) sensor, the issue persists. Interestingly, when I disconnect the MAF sensor, the engine runs normally—no noticeable change in performance. This suggests the MAF may not be the root cause. However, when I unplug the Positive Crankcase Ventilation (PCV) hose, the engine runs better temporarily; but as soon as I reconnect it, the engine dies. I tested the MAF sensor with a digital multimeter: the pink wire shows 12 volts (positive), the black wire reads good ground, and the yellow signal wire shows approximately 9 volts. However, this reading appears reversed—typically, the signal voltage should vary with load, not remain constant. I suspect the MAF is either faulty or miswired. The sensor is a three-wire unit: pink (12V power), black (ground), and yellow (signal). For accurate readings, a digital voltmeter must be set to Hz mode to measure signal frequency, not voltage. A steady 9V on the yellow wire indicates an abnormal output—this could point to sensor failure or wiring issues. I'm also wondering if the P0340 code is due to a faulty camshaft position sensor or a defective distributor (if applicable). I have already replaced both components, but the issue remains unresolved. Could you advise on how to properly diagnose these codes? Specifically: - What should the voltage be at idle on the brown/white wire? - Does a scan tool show live data and can it read all stored codes (especially P0999 and above)? - Should I clean the MAF sensor, or is an oil-based filter like K&N inappropriate for this application?
The MAF sensor has three wires: pink (12V power), black (ground), and yellow (signal). The yellow wire should be measured in Hz mode, not voltage. A steady 9V reading suggests the sensor is malfunctioning or improperly wired. Start by cleaning the MAF sensor—avoid using oil-based filters like K&N, as they can cause false readings. For P0340: Have you replaced the Camshaft Position (CMP) sensor? Or checked the distributor? Ensure it's properly installed and grounded. Confirm that the pink wire is receiving 12V at idle. Also check voltage on the brown/white wire at idle—this can indicate ignition timing or sensor health. A scan tool should display live data and show all stored codes, especially P0999 and above. Without this, it's difficult to determine if the issue is sensor-related or deeper in the engine management system.