DTC code
P0685
ECM/PCM Power Relay Control Circuit/Open
Technical guide
Symptoms
- Multiple electrical faults
- ECM not powering up fully
- possible no start
Probable causes
- ECM/PCM power relay control circuit open
- main ECM relay not being commanded
- wiring fault
- failed relay
Diagnostic steps
- Check ECM main relay.
- Test relay wiring.
- Check ECM power supply via relay.
- Replace main relay.
Cross-checked technical synthesis (QA). It does not replace the manufacturer's procedure.
AI here is a librarian: this page shows only what mechanics confirmed, or says “unknown”. It never suggests a diagnosis — MECCANIC interprets the code, never your car.
0 confirmed cases on P0685
Nothing confirmed yet for this code. No guess is offered on purpose.
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