GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2007 🢒 DTS 🢒 Power and Signal Distribution 🢒 Wiring Systems and Power Management 🢒 Horns System Description and Operation

System Description

The horn system consists of the following components:

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

System Operation
    • 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 Description

Battery positive voltage is applied at all times to the horn relay coil and the horn relay switch. Pressing the horn switch applies ground through the switch contacts and the horn relay control circuit to the coil side of the relay, energizing the relay. Battery voltage is then applied through the switch side of the relay, the horn fuse, and the horn control circuit to the horns. The body control module (BCM) may also apply ground to the horn relay control circuit as described above. The horns will sound as long as ground is applied to the horn relay control circuit.