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 pad. The horn relay should click and the horn should sound as long as the horn pad 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, very that a test lamp does not illuminate between the coil control circuit terminal and ground.

⇒	If the test lamp illuminates, test the control circuit for a short to voltage.

3. Verify that a test lamp illuminates between the coil side B+ circuit terminal and ground.

⇒	If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the HORN fuse is open, test the horn control circuit terminal for a short to ground. If the circuit tests normal, test or replace the HORN relay.

4. Verify that a test lamp illuminates between the switch side B+ circuit terminal and ground.

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

5. Ignition OFF, disconnect the harness connector at the horn assembly.
6. 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 an open/high resistance.

7. Connect the harness connector at the horn assembly.
8. Connect a 10A fused jumper wire between the switch side B+ circuit terminal and the horn control circuit terminal. Verify the horn is activated.

⇒	If the horn does not activate, test the horn control circuit for an open/high resistance. If the circuit tests normal, test or replace the horn assembly.

9. Disconnect the harness connector C2 at the steering wheel.
10. Test for less than 1.0 ohm of resistance between the horn switch ground circuit terminal A and ground.

⇒	If greater than the specified range, test the ground circuit for an open/high resistance.

11. Connect the harness connector C2 at the steering wheel.
12. Ignition ON, Connect a test lamp between the coil side B+ circuit terminal and the coil control circuit terminal.
13. Depress the horn pad. The test lamp should turn ON and OFF when pressing and releasing the horn pad.

⇒	If the test lamp is always ON, test the coil control circuit for a short to ground. If the circuit tests normal, replace the horn switch.

⇒	If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the horn switch.

14. Command the horn ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

⇒	If the test lamp is always OFF, replace the BCM.

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

Relay Test

1. Ignition OFF, disconnect the HORN relay.
2. Test for less than 200 ohms resistance between terminals 85 and 86.

⇒	If resistance is not in the specified range, replace the relay

3. Test for infinite resistance between the following terminals.

•

30 and 86

•

30 and 87

•

30 and 85

•

85 and 87

⇒	If not the specified value, replace the relay

4. Test for less than 2 ohms of resistance between terminals 30 and 87A.

⇒	If greater than the specified range, replace the relay.

5. Install a 10A fused jumper wire between relay terminal 85 and 12 volts. Install a jumper wire between relay terminal 86 and ground. Test for less than 2 ohms of resistance between terminals 30 and 87.

⇒	If greater than the specified range, replace the relay

Horn Test

1. Ignition OFF, disconnect the harness connector at the horn assembly.
2. Install a 10A fused jumper wire between the control circuit terminal B and 12 volts. Install a jumper wire between the ground terminal A and ground.
3. Observe the operation of the horn. The horn should sound.

⇒	If the horn does not sound, replace the horn assembly.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.