P0685: ECM/PCM Power Relay Control Circuit/Open
MediumPowertrainEngine Electronics
What does P0685 mean?
P0685 is a diagnostic trouble code indicating "ECM/PCM Power Relay Control Circuit/Open". This means there is an electrical break in the engine electronics wiring — a connector may be unplugged, a wire broken, or a component has failed internally. The ECU detected no signal where it expected one.
Common causes
- Damaged or corroded wiring harness
- Loose or disconnected electrical connector
- Failed engine electronics sensor or actuator
- Blown fuse in the related circuit
- Poor ground connection
What should you do?
Schedule a diagnostic appointment at your earliest convenience. The vehicle is generally safe to drive short distances, but the underlying issue should be addressed to prevent it from worsening.
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Code P0685 can mean different things depending on your vehicle. TorqueBot gives you a diagnosis specific to your make, model, and year.