Horn System: Overview Chevrolet Silverado 3500 HD

Circuit/System Description

The body control module (BCM) controls the horn relay by grounding the control circuit of the horn relay coil energizing the relay. When the horn relay is energized, the horn relay contacts close applying voltage through the horn fuse and the horn control circuit to the horns.

Battery positive voltage is applied at all times to the horn relay coil and horn relay switch. Pressing the horn switch applies ground to the horn relay control circuit. The body control module (BCM) also may apply 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 horn via the horn control circuit. The horn will sound as long as ground is applied to the horn relay control circuit.

System Description

The horn system consists of the following components

1. HORN fuse
2. Horn PCB relay
3. Horn switch
4. Horn
5. Body control module (BCM)

System Operation

1. The vehicle horns are activated whenever the horn switch is depressed.
2. The 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 (with Accessory 2 Way Remote)»(ref-317175-S05667257752009060900000) or «Keyless Entry System Description and Operation (without Accessory 2 Way Remote)»(ref-317175-S08207284942009060900000) . 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 (with Accessory 2 Way Remote)»(ref-317175-S05667257752009060900000) or «Keyless Entry System Description and Operation (without Accessory 2 Way Remote)»(ref-317175-S08207284942009060900000) . When the OnStar® system is used to sound the horns if equipped. For further information, refer to «OnStar Description and Operation»(ref-317145-S35179768822009060900000) .

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 horn through the horn control circuit. The horn will sound as long as ground is applied to the horn relay control circuit.