What does code P0685 mean?

Q: What does code P0685 mean?

ECM/PCM Power Relay Control Circuit Open. P0685 means the engine control module (ECM) or powertrain control module (PCM) has detected an open circuit in the control wire for its own power relay, so the relay cannot be commanded to supply power to the module. The computer is not reporting a failed relay directly; it is reporting that the electrical path it uses to switch that relay on is broken or not responding as expected.

DTC codes / P06xx · Computer and output circuits / P0685

P0685ECM/PCM Power Relay Control Circuit Open

P0685 means the engine control module (ECM) or powertrain control module (PCM) has detected an open circuit in the control wire for its own power relay, so the relay cannot be commanded to supply power to the module. The computer is not reporting a failed relay directly; it is reporting that the electrical path it uses to switch that relay on is broken or not responding as expected.

SystemPowertrain

Code typeGeneric (all makes)

SeverityHigh

Fix difficultyProfessional

AreaComputer and output circuits

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.