Conditions for Setting the DTC

WARNING: This page is about a different car, the 2006 Pontiac Montana SV6, 2006 Chevrolet Uplander, and 2006 Buick Terraza. However, it is still accessible from the selected car via links, so may be relevant.

The BCM detects a short to voltage or short to ground in the rear defog relay control circuit.
The BCM detects that the rear defog relay control circuit is open.
Battery positive voltage to the RR defog relay is open or shorted to ground.
The RR defog relay coil is open.
The condition above must be present for more than 1 second.