Circuit Description
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 body control module (BCM) monitors the rear fog lamp switch signal circuit in order to determine when the rear fog lamp relay is to be energized. When the BCM senses that the rear fog lamp switch signal circuit is grounded momentarily by pressing the rear fog lamp switch, the BCM energizes the rear fog lamp relay by grounding the rear fog lamp relay control circuit.