Fog/Driving Lamp: Description and Operation

FOG LAMPS

Principles of Operation
When the ignition switch is in the RUN position and the parking lamps are on, the smart junction box (SJB) provides voltage to the fog lamp relay coil. Ground for the fog lamp relay coil is controlled by the fog lamp switch. When the fog lamp switch is engaged, ground is supplied to the fog lamp relay coil. When the fog lamp relay is energized, voltage is routed to the fog lamps.

The SJB utilizes a protective circuit strategy for many of its outputs (for example, the headlamp output circuit). Output loads (current level) are monitored for excessive current (typically short circuits) and are shutdown (turns off the voltage or ground provided by the module) when a fault is detected. A continuous DTC is stored at that time for the fault. The circuit will then reset after an ignition cycle or customer demand of the function (switching the component on, 30-minute battery saver being energized). When an excessive circuit load occurs several times, the module shuts down the output until a repair procedure is performed. At the same time, the continuous DTC that was stored on the first failure will not clear by a command to clear the continuous DTCs. The module will not allow this code to be cleared or the circuit restored to normal until a successful on-demand self-test proves that the fault has been repaired. After the on-demand self-test has successfully completed (no on-demand DTCs present), the continuous DTC will have been cleared and the circuit function will return.