P0689
PowertrainPcm Powerhigh severityECM/PCM Power Relay Sense Circuit Low
What P0689 Means
The control module detected low voltage on the power relay sense circuit that monitors main relay output. This means the module isn't seeing expected voltage when the main power relay should be energized.
Symptoms
- Hard or no start
- Intermittent stalling
- Warning lights on dash
Common Causes
- Faulty main power relay
- Corroded or loose relay connector
- Wiring open or short in sense circuit
- Failing PCM/ECM
Diagnostic Steps
- Check main relay connector and pins
- Test relay operation and coil
- Measure voltage on sense circuit with relay active
- Inspect wiring for opens or shorts to ground
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