Possible causes

– Faulty ignition switch
– Ignition Switch harness is open or shorted
– Ignition Switch circuit poor electrical connection
– Faulty Engine Control Module (ECM)

When is the code detected?

The ECM has detected a voltage deifference between two circuits

Symptoms

– Engine Light ON (or Service Engine Soon Warning Light)
– Possible no crank or start

P1682 CADILLAC Description

There are 2 ignition 1 voltage circuits supplied to the Engine Control Module (ECM). The first ignition circuit is provided by the powertrain relay, through a fuse. This ignition 1 voltage circuit supplies power to all the internal ECM circuits associated with the throttle actuator control (TAC) operation. The second ignition 1 voltage circuit is supplied by the run/crank relay through a fuse, and is used to power the remaining internal ECM circuits. If the ECM detects a voltage difference between the 2 ignition 1 voltage circuits, DTC P1682 will set.

CADILLAC Technical Service Bulletins for P1682 code