Backup Lamps
WARNING: This page is about a different car, the 2003 GMC Sonoma, 2003 GMC Jimmy, 2003 Chevrolet S10 Pickup, and 2003 Chevrolet Blazer. However, it is still accessible from the selected car via links, so may be relevant.
The B/U fuse in the engine wiring harness junction block supplies battery positive voltage to the normally open backup lamp switch. When driver places the gear selector lever is in the REVERSE position, the backup lamp switch closes and the current flow is from the backup lamp switch through the VEH B/U fuse to the backup lamps. The backup lamps are grounded at G475 and G422 on the pickup and G450 on the utility.