Horn System - Operation

OPERATION

The horn system components operate on battery current received through non-switched fused B(+) circuits so that the system will remain operational, regardless of the status of the ignition switch. The Body Control Module (BCM) controls the output of battery current to the horns through a horn relay soldered to a Printed Circuit Board (PCB) located within the Power Distribution Center (PDC). The BCM controls the relay based upon internal programming as well as electronic message inputs received from the Steering Angle Sensor (SAS) or the Radio Frequency Hub Module (RFHM) (also known as the RF Hub) over the Controller Area Network (CAN) data bus.

The vehicle operator can control typical horn system signaling through the horn switch contacts within the hub cavity of the steering wheel. When the Driver AirBag (DAB) trim cover in the center of the steering wheel is depressed, it provides a hard wired analog input to the Local Interface Network (LIN) slave node integral to the LIN module or the speed control switch pod in the right horizontal spoke of the steering wheel. The LIN slave node then sends an electronic horn switch status message to the LIN master node integral to the SAS. Then the SAS, which is also a gateway to the CAN data bus, relays an electronic horn request message to the BCM over the CAN data bus.

In addition, the RFHM sends electronic horn request messages to the BCM over the CAN data bus in response to inputs received from the Remote Keyless Entry (RKE) transmitter in vehicles without the optional Passive Entry Keyless Go (PEKG) system, or received from the FOB with Integrated Key (FOBIK) transmitter in vehicles with the PEKG system. Lastly, as the Vehicle Theft Security System (VTSS) controller, the BCM can activate the horn system based upon programming and both hard wired and electronic message inputs from the various VTSS components.

The horns can be activated by the BCM to support each of the following features:
- Remote Keyless Entry System - Remote Keyless Entry (RKE) system Lock request audible verification.

- Remote Keyless Entry System - Remote Keyless Entry (RKE) system Panic mode audible alert.

- Remote Start System - Remote Start System Start request audible verification.

- Vehicle Theft Alarm - Vehicle Theft Alarm (VTA) audible alarm.

The RKE system Lock request audible verification is a customer programmable feature, which allows the feature to be enabled or disabled to suit individual preferences. Electronic Vehicle Information Center - Operation.

The hard wired circuits between components related to the horn system 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.

However, conventional diagnostic methods will not prove conclusive in the diagnosis of the horn system or the electronic controls or communication between modules and other devices that provide some features of the horn system. The most reliable, efficient and accurate means to diagnose the horn system or the electronic controls and communication related to horn system operation requires the use of a diagnostic scan tool.