Horn System - Description

DESCRIPTION

An electrically-operated horn system is standard factory-installed equipment in this vehicle. Depressing the Driver Air Bag (DAB) trim cover in the center of the steering wheel actuates the horn switch contacts, which provides the vehicle operator with a convenient, audible signaling device that can be used to alert pedestrians or the operators of other vehicles in near proximity.

The Body Control Module (BCM) (also known as the Common Body Controller/CBC) serves as the controller for the horn system, which also allows the BCM to utilize the horn system when providing audible outputs to support other vehicle features such as the horn chirp verification of the Remote Keyless Entry (RKE) and Remote Start systems, as well as the pulsing horn deterrent feature of the optional Vehicle Theft Alarm (VTA) and RKE Panic mode.

The horn system includes the following major components, which are described in further detail elsewhere in this service information:

- Horn Relay - The horn relay is soldered onto the Printed Circuit Board (PCB) located within the Power Distribution Center (PDC) and is not serviceable. The PDC is located in the left front corner of the engine compartment just forward of the battery.

- Horns - The standard dual-note horns are located on a bracket secured to the outboard side of the left front fender load beam, above the left front wheel house splash shield. The splash shield must be removed to gain access to the horns for service.

- Horn Switch - The horn switch consists of four individual sets of normally open contacts that are connected in a parallel circuit arrangement. The horn switch contacts are mounted to the steering wheel armature beneath the Driver AirBag (DAB) module within the hub area of the steering wheel.

Certain functions and features of the horn system rely upon resources shared with other electronic modules in the vehicle over a Local Interface Network (LIN) data bus as well as over the Controller Area Network (CAN) data bus. Other electronic modules in the vehicle that may affect horn system operation are:

- Body Control Module - The Body Control Module (BCM) is located on the upper left corner of the dash panel within the passenger compartment, where it is concealed behind the instrument panel to the left of the steering column and pedal support bracket. Body Control Module - Description.

- Local Interface Network Module - A LIN module is used only on vehicles that are not equipped with the optional speed control system. The LIN module is a LIN slave node that is concealed beneath the bezel on the right horizontal spoke of the steering wheel. Local Interface Network Module - Description.

- Radio Frequency Hub Module - The Radio Frequency Hub Module (RFHM) (also known as the RF Hub) is located on the cab back panel within the passenger compartment of the vehicle, where it is concealed behind the cab back trim. Radio Frequency Module (RF Hub) - Description.

- Speed Control Switch Pod - The speed control switch pod is used only on vehicles equipped with the optional speed control system. This switch pod includes an integral LIN slave node and is secured to the right horizontal spoke bezel of the steering wheel in place of the LIN module. Speed Control - Description.

- Steering Angle Sensor - The Steering Angle Sensor (SAS) is integral to the clockspring. The SAS is a Local Interface Network (LIN) master node and a gateway to the Controller Area Network (CAN) data bus. The SAS is concealed on the back of the clockspring beneath the steering column shrouds at the top of the steering column, directly beneath the steering wheel.

The SAS, the BCM and the RFHM each contain a microcontroller and programming that allow them to communicate with each other and other electronic modules in the vehicle using the Controller Area Network (CAN) data bus. In addition the LIN module, the speed control switch pod and the SAS communicate with each other using a Local Interface Network data bus. Communication - Description.

Hard wired circuitry connects the various horn system components to each other through the electrical system of the vehicle. These hard wired circuits are integral to several wire harnesses, which are routed throughout the vehicle and retained by many different methods. These circuits may be connected to each other and to the vehicle electrical system through the use of a combination of soldered splices, splice block connectors and many different types of wire harness terminal connectors and insulators. Refer to the appropriate wiring information. The wiring information includes wiring diagrams, proper wire and connector repair procedures, further details on wire harness routing and retention as well as pin out and location views for the various wire harness connectors, splices and grounds.