Exterior Lighting Systems Description And Operation

With the ignition switch in the ON position, and the park lamps or low beam headlights on, the fog lights will illuminate when the driver moves the fog lamp switch to the ON position. The underhood fuse block supplies battery positive voltage to the switch circuit of the fog lamp relay. Ignition voltage is available to the fog lamp relay control circuit. The DIM controls the fog lamp relay control circuit. When the front fog lamp switch is ON, the front fog lamp input of the instrument panel Integration Module (IPM) has ground. The IPM sends a class 2 message to the DIM, which energizes the control circuit of the front fog lamp relay. When the DIM energizes the front fog lamp relay, the current flows from the front fog lamp relay switch to both front fog lamps. The front fog lamps have ground at G401. The state of the front fog lamps (on or off) will remain the same until the front fog lamp switch is moved to the OFF position, even between ignition cycles. The park lamps or low beam headlights must be ON in order for the fog lights to be illuminated. Fog lamp operation will be cancelled whenever the park lamps, are turned OFF or the high beam headlights have been selected.

The rear fog lamps are controlled in much the same way, however the front fog lamps must be on in order to turn on the rear fog lamps. The rear fog lamps have there own relay, and both the relay control and current flow are the same.