Description And Operation
DESCRIPTION
LHD model shown. RHD model similar.
The horn system includes the following major components:
| 1. | Refer to HORN SWITCH . |
| 2. | Refer to BODY CONTROL MODULE . |
| 3. | Refer to HORN . |
An electrically-operated dual-note horn system is standard factory-installed equipment in this vehicle. The horn system features one combined low-note and high-note horn unit. The Power Distribution Center (PDC) contains the horn fuse and the horn relay. Pressing either side of the upper surface of 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.
OPERATION
The horn operates on battery current received from a horn relay located in the Power Distribution Center (PDC) through a fuse also located in the PDC. The vehicle operator can control typical horn system signaling through the horn switch within the hub of the steering wheel. When the upper surface of the Driver Air Bag (DAB) trim cover is pressed, it provides a hard-wired ground path to the Body Control Module (BCM). In response to that input the BCM uses a Low Side Driver (LSD) to provide a ground path to the control coil of the horn relay. The horn system circuit is designed so the system will remain operational, regardless of the status of the ignition switch.
The horns can also 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 - RKE system Panic mode audible alert for North American (NA) markets only.
- Remote Start System - Remote Start System Start request audible verification for NA markets only.
- Vehicle Theft Alarm - Vehicle Theft Alarm (VTA) audible alarm except in vehicles manufactured for markets where an alarm siren is required.
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, details of wire harness routing and retention, connector pin-out information and location views for the various wire harness connectors, splices and grounds. For proper wire repair, and connector repair procedures, refer to STANDARD PROCEDURE or REMOVAL or INSTALLATION .
However, conventional diagnostic methods will not prove conclusive in the diagnosis of the horn system or the electronic controls and 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.
| Refer to COMPONENT INDEX . |
When the DAB trim cover is pressed, the closed horn switch circuit provides a ground signal to the BCM, which then, using a LSD, pulls the control coil of the horn relay located within the PDC to ground. The horn relay then controls the output to the horns accordingly.
Inputs:
- Horn request from horn switch
- Accessory blink request; FOBIK safe unlock all request
- Remote start chirp
- Panic request; FOBIK RF request
- IPC setup for horn sound during lock and remote start
- Alarm system horn request
Outputs:
- Horn command to horn relay
| Refer to COMPONENT INDEX . |
The horns have a path to ground at all times through the wire harness connection to an eyelet terminal secured to the body sheet metal. The horns are completely controlled by a fused B(+) output received through a fuse and the closed contacts of the horn relay located within the PDC.
Within the two halves of the horn housing are a flexible diaphragm, a plunger, an electromagnetic coil and a set of contact points. The diaphragm is secured in suspension around its perimeter by the mating surfaces of the horn housing. The plunger is secured to the center of the diaphragm and extends into the center of the electromagnetic coil. The contact points control the current flow through the windings of the electromagnetic coil.
When the horns are energized, electrical current flows through the closed contact points to each electromagnetic coil. The resulting electromagnetic field draws each plunger and diaphragm toward it until that movement mechanically opens the contact points. When the contact points open, the electromagnetic field collapses allowing each plunger and diaphragm to return to their relaxed positions and closing the contact points again. This cycle continues repeating at a very rapid rate producing the vibration and movement of air that creates the sound that is directed through each horn trumpet outlet.
| Refer to COMPONENT INDEX . |
The horn switch allows the vehicle operator to actuate the horns by pressing anywhere on the upper surface of the DAB trim cover in the center of the steering wheel. The three sets of horn switch contacts are wired in parallel so they perform as a single switch. One wire for each pair of contacts is connected to a path to ground at all times through the steering wheel wire harness and the Steering Column Control Module (SCCM).