For 1990-2009 cars

### System Description

The horn system consists of the following components:

• | Horn relay

• | Horn switch

• | Horn assembly

• | Body control module (BCM)

• | Steering wheel coil assembly

### System Operation

Both the horn switch and body control module (BCM) may command the horns on.

The BCM controls the horn under any of the following conditions:

• | When the content theft deterrent (CTD) systems determines an alarm condition exists, the horn may sound as part of the alarm cycle.

• | When the panic button is depressed on the remote control door lock transmitter. For further information refer to Keyless Entry System Description and Operation .

• | When the keyless entry system is used to lock the vehicle, a horn chirp may sound to notify the driver that the vehicle has been locked.

The horn switch controls the horn only when the horn switch is depressed.

### Circuit Operation

Battery positive voltage is applied at all times to the horn relay coil and the horn relay switch. Pressing the horn switch applies ground to the horn switch signal circuit. The body control module (BCM) also may apply ground to the horn relay control circuit as described above. When the horn relay control circuit is grounded, the horn relay is energized and battery positive voltage is applied to the horns through the horn control circuit. The horns sound as long as ground is applied to the horn relay control circuit.