P1682 GMC - Ignition 1 Switch Circuit 2
- Ignition Switch harness is open or shorted
- Ignition Switch circuit poor electrical connection
- Faulty Engine Control Module (ECM)
- Possible no crank or start
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.