Code
P0685
ECM
ECM power relay control circuit malfunction
The ECM power relay circuit has a fault.
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Most likely causes
- Faulty ECM relay
- Wiring fault
- Failed ECM
Symptoms you may notice
- No start
- ECM not powering up
Checks to run
- Test the relay
- Check wiring
Tools you may need
Multimeter
Always diagnose before replacing. Codes share symptoms; confirm the cause with measurements before buying parts.