P0691
PowertrainCooling Fanhigh severityFan 1 Control Circuit Low
What P0691 Means
The PCM detected a low voltage condition in the cooling fan 1 control circuit. This means the fan may not run when commanded, risking engine overheating.
Symptoms
- Engine overheating
- Cooling fan not running
- Check engine light on
Common Causes
- Short to ground in fan control wiring
- Failed cooling fan relay
- Faulty cooling fan motor
- Damaged PCM output driver
Diagnostic Steps
- Scan and confirm P0691 code
- Inspect fan control wiring for shorts
- Test fan relay and motor operation
- Check PCM fan control output signal
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