GM Service Manual Online
For 1990-2009 cars only

Current for the fog lamps is supplied from the 10A FOG LP fuse located in the instrument panel fuse block. Current then flows through CKT 1140 to terminal 87 of the fog lamp relay. Current is also supplied to terminal 86 of the fog lamp relay from the headlamp switch through CKT 9. Current is only supplied when the parking or headlamps are on but loses current when the high beam head lamps are turned on. The fog lamp switch is a normally open switch that is grounded when closed. When pressed it sends a ground through CKT 192 to the body control module (BCM). The BCM then grounds CKT 1317 to terminal 85 of the relay. The relay is then actuated and sends current out through terminal 30 of the relay into CKT 34 then into the fog lamps turning them on. The lamps are individually grounded through CKT 150. After the fog lamps are turned on, the switch receives voltage back from CKT 34 to illuminate an internal LED that indicates the lamps are turned on.