Fog/Driving Lamp: Description and Operation

FOG LAMPS

Principles of Operation

NOTE: The smart junction box (SJB) is also known as the generic electronic module (GEM).

The battery junction box (BJB) provides voltage to the fog lamp relay. Ground for the fog lamp relay coil is controlled by the SJB. When the fog lamp switch is engaged, voltage is supplied to the SJB, signaling a request for fog lamps. If the ignition switch is in the RUN position, the SJB provides ground for 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 shut down (turns off the voltage or ground provided by the module) when a fault is detected. A continuous DTC is stored at that time of the fault. The circuit then resets 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 carried out. At the same time, the continuous DTC that was stored on the first failure cannot be cleared by a command to clear the continuous DTCs. The module does 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 clears and the circuit function returns.