Backup Lamps - Automatic Transmission

WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

The backup lamp request signal is sent from the powertrain control module (PCM) to the body control module (BCM) on the class 2 message system. This signal is based on the park/neutral position (PNP) switch signal. The BCM supplies voltage on the backup lamp supply voltage circuit to the backup lamps and to the automatic day/night mirror. Voltage for the courtesy lamp supply voltage circuit and backup lamp supply voltage circuit is from the TBC B fuse in the instrument panel (I/P) fuse block directly through the BCM to these circuits. A short to ground on either of these circuits will open the fuse. The backup lamps are grounded at G401.

For trailer wiring, a separate backup lamp circuit is connected through the underhood fuse block from the TRLR B/U 10-amp fuse to the trailer wiring harness.