ECM/PCM Power Relay Sense Circuit/Open
A relay powers the engine ECU and its components when you switch the ignition on.
What the car has detected
The ECU does not get the voltage that should come through the relay: fuse, relay or wiring.
It may leave the fan running with the car switched off and drain the battery, or cause starting faults. Have it checked soon.
Symptoms
- Engine warning light on
- Fan at full speed with the car off and cold
- Battery running flat
Possible causes
- Blown fuse
- Faulty ECU power supply relay
- Broken or shorted wire, or a loose or corroded connector
Checks for the garage
- Check the circuit fuse
- Test or swap the power supply relay
- Check the wiring between the relay and the ECU
Next step
Ask for the fuse, the ECU power relay and its wiring to be checked.
Go to a garage soon. If the fan keeps running with the car off, disconnect the battery so it does not go flat.