For 1990-2009 cars

### System Description

The horn system consists of the following components:

• | The HORN fuse

• | The horn relay

• | The horn switch

• | The horn assembly

• | The body control module (BCM)

### System Operation

The vehicle horn system is activated under the following conditions:

• | The horn switch is depressed.

• | The BCM commands the horns on. The BCM commands the horns on under any of the following conditions:

- | When the content theft deterrent system detects a vehicle intrusion--For further information refer to Content Theft Deterrent (CTD) Description and Operation .

- | 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 OnStar® system is used to sound the horns, if equipped--For further information refer to OnStar Description and Operation .

- | When the unlock button on the keyless entry transmitter is pressed, a horn chirp will sound to notify the driver that the vehicle has been unlocked. For further information refer to Keyless Entry System Description and Operation

- | When the lock button on the keyless entry transmitter is pressed twice within 5 seconds, a horn chirp will sound to notify the driver that the vehicle has been locked. For further information refer to Keyless Entry System Description and Operation .

### 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 relay control circuit. The BCM may also 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.