P0642
PowertrainPcm Referencemoderate severitySensor Reference Voltage A Circuit Low
What P0642 Means
The PCM detected the sensor reference voltage on circuit A is below normal. Sensors relying on this reference may report faulty values.
Symptoms
- Multiple sensor fault codes
- Check engine light on
- Poor engine performance
Common Causes
- Short to ground on reference circuit
- Faulty sensor pulling reference down
- Damaged wiring
- Faulty PCM
Diagnostic Steps
- Measure reference voltage at sensors
- Inspect wiring for short to ground
- Disconnect sensors one at a time to isolate
- Repair circuit or replace PCM
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