Conditions for Setting the DTC

WARNING: This page is about a different car, the 2004 Chevrolet Corvette. However, it is still accessible from the selected car via links, so may be relevant.

The BCM detects a high voltage level (a short to voltage or BCM open internally) in the backup lamp relay control circuit.
The BCM can only test for this condition with the backup lamp relay energized.
All conditions must be present for 2 seconds.