8H - Horn

DESCRIPTION
OPERATION

DESCRIPTION

An electrically-operated horn system is standard factory-installed equipment in this vehicle. A single note system is standard for vehicles manufactured for domestic markets, while a dual note system is used in vehicles manufactured for most export markets. Through the horn switch, either horn system provides the vehicle operator with a convenient, audible signaling device that can be used to gain the attention of pedestrians or to alert other vehicles in close proximity.

On vehicles so equipped, the horn system can also be activated by the Totally Integrated Power Module (TIPM) in response to certain electronic requests from other systems in the vehicle. The Remote Keyless Entry (RKE) system can provide a customer programmable audible horn chirp verification that a valid LOCK request was received from the RKE transmitter. The horn system provides the RKE system PANIC mode audible alert or deterrent on vehicles so equipped. The horn system also serves as the Vehicle Theft Security System (VTSS) audible alarm.

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

Horn - A low-note horn is located on the back of the Front End Module (FEM) carrier in the engine compartment, directly behind the left head lamp unit in all vehicles. A high-note horn is located on the back of the front bumper support beam, just inboard of the right frame rail on vehicles so equipped.
Horn Switch - A floating-type horn switch is located on the back of the driver airbag housing and is secured to the steering wheel armature with two screws.

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:

ElectroMechanical Instrument Cluster - The ElectroMechanical Instrument Cluster (EMIC) (also known as the Cab Compartment Node/CCN) is located in the instrument panel, directly in front of the driver. In addition to instrumentation, the EMIC provides many electronic interior body control functions and is a Local Interface Network (LIN) master node as well as a gateway to the Controller Area Network (CAN) data bus. (Refer to 08 - Electrical/8J - Instrument Cluster - Description) .
Speed Control Switch Pod - The speed control switch pod in the right horizontal spoke bezel of the steering wheel includes a Local Interface Network (LIN) slave node that monitors and transmits the status of the horn switch. (Refer to 08 - Electrical/8P - Speed Control/SWITCH, Speed Control - Description) .
Totally Integrated Power Module - The Totally Integrated Power Module (TIPM) is located in the engine compartment, near the battery. The TIPM also communicates with other electronic modules on the CAN data bus network. (Refer to 08 - Electrical/8W - Wiring/Power Distribution/MODULE, Totally Integrated Power (TIPM) - Description).

The EMIC and the TIPM each contain a microprocessor and programming that allow them to communicate with each other using the Controller Area Network (CAN) data bus. In addition the speed control switch pod and the EMIC communicate with each other using a Local Interface Network data bus. (Refer to 08 - Electrical/8E - Electronic Control Modules/COMMUNICATION - Description) .

Hard wired circuitry connects the horn system components to 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, to the vehicle electrical system and to the horn system components 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.

OPERATION

The horn system operates on battery current received from an output of the Totally Integrated Power Module (TIPM) through a high side driver. The horn system circuit is designed so that the system will remain operational, regardless of the ignition switch position.

The vehicle operator can control typical horn system signaling through the horn switch within the hub of the steering wheel. When the Driver AirBag (DAB) trim cover is depressed, it provides a hard wired analog input to the Local Interface Network (LIN) slave node integral to the speed control switch pod. The LIN slave node then sends electronic horn switch status messages to the LIN master node integral to the ElectroMechanical Instrument Cluster (EMIC) (also known as the Cab Compartment Node/CCN). The EMIC then relays an electronic horn request message to the Totally Integrated Power Module (TIPM) over the Controller Area Network (CAN) data bus.

In addition, the Remote Keyless Entry (RKE) system will send electronic horn request messages to the TIPM over the CAN data bus in response to inputs received from the RKE transmitter through the Wireless Control Module (WCM) (also known as the Sentry Key REmote Entry Module). Lastly, as the Vehicle Theft Security System (VTSS) controller, the TIPM can activate the horn system based upon programming and both hard wired and electronic message inputs from the various VTSS components.

The hard wired inputs and outputs for the horn system 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 speed control switch pod, the EMIC, the WCM, the TIPM or the electronic controls or communication between other modules and devices that provide features of the horn system. The most reliable, efficient, and accurate means to diagnose the speed control switch pod, the EMIC, the WCM, the TIPM or the electronic controls and communication related to horn system operation requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.