Principles Of Operation

PRINCIPLES OF OPERATION

The horn relay B+ power and the horn relay switched power are supplied through circuit 1682 (RD/LB). The horn relay is controlled by the horn switch. The horn relay is grounded through the horn switch by circuit 6 (YE/LG). When the horn switch is pressed, the horn relay control circuit 6 (YE/LG) is grounded. The relay is then closed causing B+ voltage to be applied to circuit 1 (DB), sounding the horn.

The horn relay is powered on both the control and controlled sides by circuit 1682 (RD/LB). When the horn switch is pressed, the horn relay control circuit 6 (YE/LG) is grounded through the horn switch. The horn relay is then energized, allowing battery voltage to flow through the horn relay to the horn through circuit 1 (DB), enabling the horn to sound. When the vehicle security system is armed, the smart junction box (SJB) provides a momentary ground to the horn relay control side to indicate the system is armed, and a continuous ground when an intrusion is detected.

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 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.