OBD-II code · Powertrain (generic)
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.
Is it safe to drive with P0685?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyOpen in relay control or harness
- Less likelyPin pushed back out of connector body
- Less likelyCracked solder joint inside the module or sensor
Symptoms
- Check engine light on
- Possible limp mode or no-start
- Multiple follow-up faults across modules
- Reset/relearn may be needed after repair
Repair at a glance
- Difficulty
- Medium
- DIY friendly
- Often, with basic tools
- Typical labour
- 0.5–1.8 h
- Emissions test
- Usually unaffected
- Parts involved
- Ecm Power Relay
Related codes
- P0682Cylinder 12 Glow Plug Circuit Open
- P0683Glow Plug Control Module 1 to PCM Communication Circuit
- P0684Glow Plug Control Module 1 to PCM Communication Range or Performance
- P0686ECM/PCM Power Relay Control Circuit Open
- P0687ECM/PCM Power Relay Sense Circuit Open
- P0688ECM/PCM Power Relay Sense Circuit High
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.