Fog Lamps

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.

With both the ignition switch in the RUN position, and the park lamps ON, the fog lights will illuminate when the driver depresses the fog lamp switch. The FOG LPS 15-amp fuse in the underhood fuse block supplies battery positive voltage to the fog lamp relay switch and coil. With the headlamp switch in either the park or headlamp position, and the fog lamp switch is in the ON position, the body control module (BCM) will energize the fog lamp relay control circuit. The BCM receives the park lamp ON signal from the interior park lamps supply voltage signal circuit. The current flow is from the fog lamp relay to both front fog lamps and to ground G100. The state of the fog lamps will remain the same until the fog lamp switch position is changed, or the ignition switch is cycled OFF and ON. Fog lamp operation will be cancelled whenever the park lamps, are turned OFF or the high beam headlights have been selected.

The rear fog lamps are controlled in much the same way, however the front fog lamps must be on in order to turn on the rear fog lamps. The SEO 1 15-amp fuse in the underhood fuse block supplies battery positive voltage to the rear fog lamp relay switch and coil. Both the relay control and current flow are the same as the front fog lamps with the exception of the rear fog lamp ground at G402.