P0685 — ECM/PCM Power Relay Control Circuit/Open

P0685: Concerns the control circuit of the engine/powertrain control-module power relay, including an open circuit.

Meaning, symptoms, causes and checks

Concerns the control circuit of the engine/powertrain control-module power relay, including an open circuit. It is a relay-control definition rather than proof of an internal ECM or PCM failure.

Affected system: ECM/PCM power relay

Symptoms

  • Difficult starting or no start; engine stalling.

Possible causes

  • Faulty relay, corroded socket, blown fuse or broken wiring.

What to check

  • Check relay, supply, continuity to ECM/PCM and grounds.

Also written as: P0685-00, P068500, PO685 (some scan tools add the fault-type byte, e.g. -00).