Horns Inoperative

Horns Inoperative

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions provides an overview of each diagnostic category.

Diagnostic Fault Information





Circuit/System Description

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.

Diagnostic Aids

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

Circuit/System Verification

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.

Circuit/System Testing

1. Ignition OFF, remove 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.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests

* Inflatable Restraint Steering Wheel Module Coil Replacement
* Horn Replacement
* Relay Replacement (Attached to Wire Harness) Relay Replacement (Within an Electrical Center)
* Control Module References for BCM replacement, setup and programming Programming and Relearning