P0689high severityPowertrain
ECM/PCM Power Relay Sense Circuit Low
on 2005-2011 Audi A6 4.2L V8 · AWD
What this code 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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