Possible causes

– Loose or poor battery terminal connection
– Low battery charge
– ECM power supply circuit is open or shorted
– ECM Programing
– Faulty ECM

Tech notes

Check the PCM fuse, if fuse is OK try erasing the code first and if the code comes back you may have to reprogram or replaced the PCM.

When is the code detected?

Indicates the PCM has experienced an internal memory fault.

Symptoms

– Engine Light ON (or Service Engine Soon Warning Light)
– Engine may not start

P0604 SUBARU Description

The PCM continuously monitors its own internal memory status, internal circuits, and output signals transmitted to the throttle actuator. This self-check insures that the PCM is functioning properly. If any malfunction is detected, the ECM will set the code and illuminate the engine light.