Fog/Driving Lamp: Description and Operation

Vehicles equipped with optional front fog lamps include a front fog lamp relay installed in the PDC, and a front fog lamp switch integral to the headlamp switch on the instrument panel. The front fog lamps have a path to ground at all times through their connection to the headlamp and dash wire harness. The left headlamp and dash wire harness has takeouts with eyelet terminals that are secured by ground screws to the left inner fender support within the engine compartment. The EMIC monitors a hard wired multiplex input from the headlamp switch to determine whether the fog lamps are selected, then sends electronic fog lamp switch status messages to the FCM over the PCI data bus.

When the FCM receives a fog lamp status message it then controls front fog lamp operation by energizing or de-energizing the front fog lamp relay control coil. The FCM also sends the appropriate electronic message back to the EMIC to illuminate or extinguish the front fog lamp indicator. When the front fog lamp relay is energized, it provides battery voltage from a fused B(+) fuse in the PDC to the fog lamps through the fog lamp relay output circuit. The FCM will automatically de-energize the front fog lamps relay any time the headlamp high beams are selected. The EMIC also provides a battery saver (load shedding) feature for the front fog lamps, which will turn these lamps off if they are left on for more than about five minutes with the ignition switch in the Off position. Each front fog lamp includes an integral adjustment screw to be used for static aiming of the fog lamp beams.