ECM/PCM Power Relay Control Circuit/Open
Power relay control circuit for the ECM/PCM is open or malfunctioning.
Heads up: this code wasn't in our hand-written library yet, so DiagCoach AI built this page on the fly. Double-check critical specs against service info before condemning parts.
What it means (plain English)
The computer that controls the engine isn't getting enough power because the relay that turns it on isn't working right.
What the computer is actually seeing
The engine control module (ECM) is not receiving the proper voltage due to an open circuit in the relay control circuit, leading to a potential no-start condition.
What a healthy reading looks like
The ECM should receive at least 12 volts when the ignition is turned on and the relay is energized.
Guided diagnostic — the DiagCoach way
Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.
- 11. Check the main relay and ensure it clicks when the ignition is turned on. If not, replace the relay. Decision: Does it click? Yes - Go to step 2. No - Replace relay and retest.
- 22. Use a multimeter to test for voltage at the power relay control circuit. Expected value: at least 12V. Decision: Is voltage present? Yes - Go to step 3. No - Check wiring from ECM to relay for damage or disconnections.
Common causes
- Faulty ECM/PCM power relay
- Wiring issues (broken or shorted wires)
- Corroded or loose connectors
- Faulty ECM/PCM
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It’s not safe to drive; you might experience no-start issues.
Will this code come back after clearing?
If the underlying issue isn’t fixed, yes, it will likely return.
Why does this code pair with P0685?
Both codes relate to the power relay control circuit and can indicate similar issues with power delivery to the ECM.
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