Possible causes

– Fualty ECM
– Wrong ECM for vehicle
– Service program error

When is the code detected?

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

Symptoms

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

P1681 CADILLAC Description

This diagnostic trouble code (DTC) indicates a programming error within the control module.