Horns Inoperative for Chevrolet Malibu 2004

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 diagnosing a Horn - Poor Tone condition, inspect the following:

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 and release the horn switch. The horn should sound.

⇒	If the horn does not sound, refer to Horn Inoperative From Horn Switch Test.

2. Perform the Horn Inoperative From BCM Test

Horn Inoperative From Horn Switch Test

1. Disconnect the HORN relay.
2. Ignition ON, verify that a test lamp illuminates between the relay coil B+ circuit and ground.

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

3. Verify that a test lamp illuminates between the relay switch B+ circuit and ground.

⇒	If the test lamp does not illuminate, test the relay switch B+ circuit for an open/high resistance.

4. Connect a 15 A fused jumper wire between the relay switch B+ circuit and the relay controlled output circuit. Verify the horn is activated.

⇒	If the horn does not activate, test the relay controlled output circuit for an open/high resistance. If the circuit tests normal, perform the Horn Test.

5. Connect a test lamp between the relay coil B+ circuit and the relay coil control circuit.
6. Press and release the steering wheel horn pad. The test lamp should turn ON and OFF when changing between the commanded states.

⇒	If the test lamp is always OFF, test the relay coil control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, perform the Horn Switch Test.

7. If all circuits test normal, test or replace the HORN relay.

Horn Inoperative From BCM Test

Replace the BCM.

Horn Test

1. Ignition OFF, disconnect the harness connector at the horn.
2. Test for less than 1.0 ohm of resistance between the horn ground circuit terminal A and ground.

⇒	If greater than the specified range, test the ground circuit for a high resistance.

3. If all circuits test normal, test or replace the horn.

Horn Switch Test

1. Ignition OFF, disconnect the harness connector at the horn switch.
2. Test for less than 1.0 ohm of resistance between the horn switch ground circuit ground.

⇒	If greater than the specified range, test the ground circuit for a high resistance.

3. If all circuits test normal, test or replace the horn switch.

Horn

1. Ignition OFF, disconnect the harness connector at the horn.
2. Install a 15A fused jumper wire between the control circuit terminal B and 12 volts.
3. Install a jumper wire between the ground circuit terminal A and ground. Verify the horn emits a clear and even tone.

⇒	If the sound emitted is not clear and even, replace the horn.