GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2002 🢒 TrailBlazer - 2WD 🢒 Body and Accessories 🢒 Horns 🢒 Horns System Description and Operation

System Description

The horn system consists of the following components:

    • The BATTERY fuse
    • The HORN fuse
    • The horn relay
    • The horn switch
    • The horns
    • The body control module (BCM)

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 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 OnStar® system is used to sound the horns (if equipped.) For further information refer to OnStar 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 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. 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.