GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2003 🢒 CTS 🢒 Body and Accessories 🢒 Horns 🢒 Horns System Description and Operation

System Description

The horn system consists of the following components:

    • HORN fuse
    • RADIO fuse
    • Horn relay
    • Inflatable restraint steering wheel coil
    • Horn switch
    • Horns
    • Body control module (BCM)
    • Steering wheel radio control switch

System Operation

The vehicle horn system is activated under the following conditions:

    • The horn switch is depressed.
    • The body control module (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 in Theft Deterrent.
      • 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 in Keyless Entry.
      • When the OnStar® system is used to sound the horns if equipped. For further information, refer to OnStar Description and Operation in Cellular Communications.

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.