Circuit Description
WARNING: This page is about a different car, the 2002 GMC Sierra, 2002 GMC Cab & Chassis Sierra, 2002 Chevrolet Silverado, and 2002 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
The FOG LPS 15 A fuse in the engine wiring harness junction block supplies battery positive voltage to the fog lamp relay switch in the engine wiring harness junction block. The headlamp switch supplies battery positive voltage to the fog lamp relay coil. With the headlamp switch in either the park or headlamp position, and the fog lamp switch pressed, the body control module (BCM) will ground the fog lamp relay control circuit. The current flow is from the fog lamp relay to both front fog lamps and to ground G100.
If the driver selects high beam headlights, a high beam input is sent to the BCM by the dimmer switch. In response to this input the BCM de-energizes the fog lamp relay.