Principles of Operation

PRINCIPLES OF OPERATION

For vehicles equipped with an automatic transaxle, the smart junction box (SJB) receives transmission gear status from the instrument cluster over the communication network. When a message is sent over the communication network stating the transaxle is in REVERSE, the SJB energizes an internal relay which supplies voltage to the reversing lamps.

For vehicles equipped with a manual transaxle, the SJB sends a voltage reference signal to the reversing lamp switch. When the transaxle is placed in reverse, the reference signal is routed to ground. When the SJB detects the transaxle is in REVERSE, the SJB energizes an internal relay which supplies voltage to the reversing 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 diagnostic trouble code (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 service 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.