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.

If the horn sounds when the horn switch is pressed but does not sound when commanded ON with the scan tool, replace the BCM.

Schematic Reference

Horn Schematics

Connector End View Reference

Horn Connector End Views

Description and Operation

Horns System Description and Operation

Electrical Information Reference

Scan Tool Reference

1. Press the horn switch. The horn relay should click and the horn should sound as long as the horn is pressed.
2. Turn ON the ignition. With a scan tool, command the BCM Horn Output. The horn relay should click and the horn should sound while commanded ON and stop sounding when commanded OFF.

1. Ignition OFF, disconnect the horn relay.
2. Ignition ON, verify that a test lamp illuminates on the coil side and switch side of the relay when connected between the horn relay supply voltage circuit and ground.

⇒	If the test lamp does not illuminate, repair the circuit for a short to ground or an open/high resistance.

3. Verify that the horn sounds with a 15-amp fused jumper connected between the horn relay supply voltage circuit and the horn control circuit.

⇒	If the horn does not sound, test for an open or high resistance on the horn control circuit and the horn ground circuit. If the circuit/connections test normal replace the horn assembly.

4. Disconnect the horn switch connector and ground the horn relay control circuit.
5. Verify that a test lamp illuminates when connected between the horn relay supply voltage circuit and the horn relay control circuit.

⇒	If the test lamp does not illuminate, test for a short to voltage, open or high resistance in the steering wheel coil assembly and the horn relay control circuit. If the circuit/connections test normal replace the BCM.

6. Remove the ground and reconnect the horn switch.
7. Verify that the test lamp illuminates when the horn switch is pressed.

⇒	If the test lamp does not illuminate, test for an open or high resistance in the steering wheel coil assembly and the ground circuit. If the circuit/connections test normal repair the open/high resistance in the horn switch.

8. Test or replace the horn relay.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.