Possible causes

– Engine Control Module (ECM) programm error
– Wrong Engine Control Module (ECM)
– Faulty Engine Control Module (ECM)

Tech notes

This code means that there may be an internal problem with the Engine Control Module (ECM). Start by checking battery charge and connections. Try clearing the code and re test.

Symptoms

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

P1680 GMC Description

The Engine Control Module (ECM) program does not recognize the vehicles id, or the id is missing in the ECM.

GMC Technical Service Bulletins for P1680 code