Description And Operation: Operation

The horn relay within the Power Distribution Center (PDC) switches battery current to the horns when the Body Control Module (BCM) energizes the electromagnetic coil of the relay using a High Side Driver (HSD). When the electromagnetic relay coil is energized, it draws and holds the normally open movable contact of the relay against the fixed relay contact. The closed relay contacts supply fused battery current from the PDC to energize the horns.

When the BCM de-energizes the electromagnetic relay coil, spring pressure returns the movable contact to the normally open position, which de-energizes the horns. The resistor within the relay is connected in parallel with the electromagnetic coil, and helps to dissipate voltage spikes that are produced when the coil is de-energized.

The hardwired inputs and outputs of the horn relay in the PDC and the BCM may be diagnosed using conventional diagnostic tools and procedures. Refer to the appropriate wiring information. However, conventional diagnostic methods will not prove conclusive in the diagnosis of the BCM or the electronic controls and communication between modules and other devices that provide some features of the BCM controlled horn relay. The most reliable, efficient and accurate means to diagnose the BCM or the electronic controls and communication related to BCM controlled horn relay operation requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.