P0687
PowertrainPcm Powerhigh severityECM/PCM Power Relay Control Circuit High
What P0687 Means
The PCM detects a high voltage condition in the ECM/PCM power relay control circuit. This may indicate a short to voltage or a failed relay.
Symptoms
- Intermittent stalling
- No-start condition
- Power relay stays energized
Common Causes
- Short to voltage in control circuit
- Faulty power relay
- Wiring insulation damage
- PCM fault
Diagnostic Steps
- Check control circuit for high voltage
- Inspect wiring for short to power
- Test power relay operation
- Verify PCM output signals
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