Switch, Horn: Operation

The floating horn switch allows the vehicle operator to actuate the horns by depressing anywhere on the upper surface of the Driver Airbag (DAB) trim cover in the center of the steering wheel. When the DAB trim cover is depressed, the DAB housing compresses the coil springs isolating one or more of the horn switch contact sets causing at least one of the four pairs of electrically conductive contacts to close. When the DAB trim cover is released, the coil springs on the switch plate return the DAB to its at rest position and open the horn switch contacts, which opens the horn switch circuit.

The four sets of horn switch contacts are wired in parallel so they perform as a single switch. One contact from each switch receives source current through an internal pull-up of the microcontroller within the Steering Column Control Module (SCCM). When the switch contacts are closed the SCCM input is pulled down to ground. The SCCM microcontroller then sends an electronic horn switch status  message to the Body Control Module (BCM) over the Controller Area Network (CAN) data bus. The BCM then controls the output to the horn relay within the front Power Distribution Center (PDC) accordingly.

The hard wired circuits between components related to the horn switch may be diagnosed using conventional diagnostic tools and procedures. Refer to the appropriate wiring information. The wiring information includes wiring diagrams, proper wire and connector repair procedures, details of wire harness routing and retention, connector pin out information and location views for the various wire harness connectors, splices and grounds.