Possible causes

– Powertrain Control Module (PCM) not programed
– PCM program
– Faulty PCM
– Wrong PCM

Symptoms

– Engine Light ON (or Service Engine Soon Warning Light)

P0602 GMC Description

This diagnostic trouble code (DTC) indicates that the Powertrain Control Module (PCM) internal EEPROM is not flashed with any vehicle software. If you install a service PCM and do not flash the EEPROM, the engine will not run. This DTC indicates that an un-flashed PCM causes the engine cranks but will not run situation.