GM Service Manual Online
For 1990-2009 cars only

The fog lights are controlled by the body control module (BCM) via the fog LP relay when the headlamp and panel dimmer switch is the head or park position.

The relay coil is powered by the output of the park lamp relay. The contact of the relay are hot at all times and is powered by the FOG LPS fuse. The BCM turns the fog lights on based on the input of the fog lamp switch on CKT 192 and the park lights on. With switch closed, grounding CKT 192, the BCM will supply a ground on CKT 1317, energizing the fog lamp relay. The fog lights receive current on circuit 34 and ground is supplied on CKT 150 to G100.

Some circuits are monitored by the BCM, and upon failure may set a DTC.