Possible causes

– Engine Control Module (ECM) Harness power supply circuit is open or shorted
– Engine Control Module (ECM) Programming
– Faulty Engine Control Module (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

P0606 GMC Description

The Engine Control Module (ECM) continuously monitors its internal memory status, internal circuits, and output signals to the throttle actuator. This self?check insures that the ECM is functioning properly. If any malfunction is detected, the ECM will set the code and illuminate the engine light.

GMC Technical Service Bulletins for P0606 code