Possible causes

– Faulty Powertrain Control Module (PCM)
– PCM harness is open or shorted
– PCM circuit poor electrical connection
– PCM Programming

Tech notes

Check the Powertrain Control Module (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 Powertrain Control Module (PCM) has experienced an internal memory fault.

Symptoms

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

P0604 GMC Description

The Powertrain Control Module (PCM) performs an internal self-test on it’s Random Access Memory (RAM) or read/write memory. If this self-test fails, the P0604 code will set.

GMC Technical Service Bulletins for P0604 code