With the headlamp switch in the HEAD or PARK position, voltage is applied to the fog lamp switch. When the fog lamp switch is closed, voltage is applied to the fog lamp relay (coil), energizing the relay as long as the headlamp dimmer switch is in the low beam position.
When the high beams are activated, ground is removed from the ground side of the fog lamp relay (coil), de-energizing the relay and turning off the fog lamps.
With the headlamp switch in the HEAD position, voltage is applied to the rear fog lamp relay (switch). When the front foglamp switch is turned on, voltage is applied to the rear fog lamp relay (coil). When the rear fog lamp switch is turned on (closed), voltage is applied to the BCM. When the BCM receives this input ground, the BCM sends a ground signal to the rear fog lamp relay (coil). When the rear fog lamp relay receives this ground, the coil is energized, closing the internal switch. Voltage is supplied to turn on the rear fog lamps.