GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2005 🢒 DeVille 🢒 Vehicle Control Systems 🢒 Vehicle DTC Information 🢒 Horns System Description and Operation

System Description

The horn system consists of the following components:

    • Dash integration module (DIM)
    • Horn fuse
    • Horn relay
    • Horn switch--The horn switch is part of the inflatable restraint steering wheel module.
    • Horns
    • Remote control door lock receiver module (RCDLR)
    • Vehicle interface unit (VIU)

System Operation

The vehicle horns are activated under the following conditions:

    • The horn switch is depressed.
    • When the OnStar® system is used to sound the horns, if equipped. For further information refer to OnStar Description and Operation in Cellular Communications.
    • The remote control door lock receiver (RCDLR) module commands the horns on. The RCDLR module 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 panic button is depressed on the remote control door lock transmitter--For further information, refer to Keyless Entry System Description and Operation in Keyless Entry.
       - 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.

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. 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.

For panic key fob operation--When the remote control door lock receiver (RCDLR) receives a panic key fob command, the RCDLR module sends a class 2 message to the dash integration module (DIM). The DIM then applies a ground to the horn relay. This energize the relay and allows voltage to be applied from the horn fuse, through the relay to the horns. Ground for the horns is applied at all times from G104.