Powertrain
generic / SAE
P0685
ECM or PCM Power Relay Control Circuit Open
The control circuit of the main ECM/PCM power relay is open - the ECU can lose power on shutdown sequence or fail to wake up at next start.
SystemPowertrain
Typegeneric / SAE
GroupP0
Range / number6 / 85
Possible causes
- Open in relay control or harness high
- Pin pushed back out of connector body low
- Cracked solder joint inside the module or sensor low
Symptoms
- Check engine light on
- Possible limp mode or no-start
- Multiple follow-up faults across modules
- Reset/relearn may be needed after repair
Inspection / repair
- Difficulty: medium
- DIY: possible
- Estimated cost: 80–350 €
- Estimated time: 0.5–1.8 h
- Component: ecm power relay
- MIL / check engine light
Sources
References
sae:J2012