GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2008 🢒 XLR 🢒 Body Systems 🢒 Horns 🢒 Horns System Description and Operation

System Description

The horn system consists of the following components:

    • HORN fuse
    • Horn relay
    • Horn switch
    • Horn assembly
    • Body control module (BCM)

System Operation

The vehicle horn system is activated under the following conditions:

    • The vehicle horns are activated whenever the horn switch is depressed.
    • The body control module (BCM) commands the horns ON under any of the following conditions:
       - 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 content theft deterrent system detects a vehicle intrusion. For further information refer to Content Theft Deterrent (CTD) 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 notification feature may be enabled or disabled through personalization. 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.

Circuit Operation

Battery positive voltage is applied at all times to the horn relay coil and the horn relay switch. Pressing either of the horn switches applies ground to the horn relay control circuit. The body control module (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.