P0685: ECM/PCM Power Relay Control Circuit/Open
Short answer: P0685 means “ECM/PCM Power Relay Control Circuit/Open”. It is a standard OBD-II code, so the basic meaning is the same on every car. Below is what it means on each of the 5 cars we cover, with a link to the full page for each car.
Standard OBD-II code Same meaning on all cars (SAE J2012).
P0685 on each car
| Car | Meaning on this car | Confidence |
|---|---|---|
| Toyota Corolla (11th gen, E170) | ECM/PCM Power Relay Control Circuit/Open | medium |
| Toyota Corolla (10th gen, E140) | ECM/PCM Power Relay Control Circuit/Open | medium |
| Honda City (5th gen, GM2) | ECM/PCM Power Relay Control Circuit/Open | medium |
| Honda Civic (10th gen, FC) | ECM/PCM Power Relay Control Circuit/Open | medium |
| Suzuki Wagon R (Pakistan, K10B) | ECM/PCM Power Relay Control Circuit/Open | medium |
Symptoms
- Check engine light on
Likely causes
- Potential causes for this code to set are
- A defective PCM power relay
- A blown fuse or fusible link
- Corroded or damaged wiring or wiring connectors (especially near the PCM relay)
- Faulty ignition switch
- Partially or totally disconnected electrical terminal at the ignition switch
- Loose or corroded battery cable ends
What to check, in order
- Check all battery and ECM power and earth connections first
- Read every stored code; an ECM fault is rare, wiring faults are common
- Have a specialist confirm before replacing the ECM
Causes and checks above are the general meaning. The exact test steps and values differ by car: open your car’s page.