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 low voltage level (an open or a short to ground) in the backup lamp relay control circuit.
The BCM can only test for this condition with the backup lamp relay de-energized.
The condition must be present for 2 seconds.