Battery voltage is supplied to the FOG LAMP relay coil through CKT 317 with the headlamp and the instrument panel lamp dimmer switch in the HEAD or the PARK position, and the fog lamp switch in the ON position. The coil is grounded through the high beam filaments through CKT 11. The relay energizes and applies voltage to the fog lamps through CKT 34. Since the coil of the FOG LAMP relay is grounded through the high beam filaments, the relay will de-energize any time the high beams are ON because equal voltage is applied to both sides of the relay coil. The daytime running lamp (DRL) control module applies voltage through CKT 9 to the fog lamp switch and to the exterior lights when the headlamp and the instrument panel lamp dimmer switch is in the OFF position.

The rear fog lamp module requires the headlamps to be ON in order to turn ON the rear fog lamps. When the headlamps are on, battery voltage is applied to the rear fog lamp module through CKT 10. The rear fog lamp switch is a momentary contact switch that, when pressed, provides a ground signal from CKT 1450, through the rear fog lamp switch, through CKT 1977 to the rear fog lamp module. When the rear fog lamp module receives the momentary ground input on CKT 1977 and the headlamps are ON, the rear fog lamp module provides the ground to the rear fog lamp relay through CKT 1870. The rear fog lamp relay is now energized and provides battery voltage through CKT 122 to the rear fog lamps. If the rear fog lamp switch is pressed again, while the headlamps are ON, the rear fog lamp module will remove the ground to the rear fog lamp relay and turn the rear fog lamps OFF. If the headlamps are turned OFF while the rear fog lamps are on, the rear fog lamps will turn off also. If the headlamps are turned back ON, the rear fog lamps will not turn on unless the rear fog lamp switch is pressed again.