Fog/Driving Lamp: Description and Operation

Vehicles equipped with optional front fog lamps include 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 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 TIPM over the CAN data bus.

When the TIPM receives a fog lamp status message it then controls front fog lamp operation by providing a battery voltage output to the fog lamps through the fog lamp feed circuit. The TIPM also sends the appropriate electronic message back to the EMIC to illuminate or extinguish the front fog lamp indicator. The TIPM will automatically deenergize the front fog lamps any time the headlamp high beams are selected. The TIPM 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 eight minutes with the ignition switch in the Lock position. Each front fog lamp includes an integral adjustment screw to be used for static aiming of the fog lamp beams.