Volt

Horns Malfunction

Battery positive voltage is applied at all times to the horn relay coil and the horn relay switch. Pressing the horn switch provides system voltage to the switch contacts and the horn relay control circuit to the coil side of the relay, energising the relay. Battery voltage is then applied through the switch side of the relay, the horn fuse, and the horn control circuit to the horns. The body control module (BCM) may also apply system voltage to the horn relay control circuit as described above. The horns sound as long as ground is applied to the horn relay control circuit.

A short to ground in the HORN relay control circuit or a short to voltage in the horn control circuit will cause the horns to sound continuously until the horns overheat and become inoperative.

Rotate the steering wheel while pressing the horn pad to identify intermittent and poor connections within the steering column.

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

Schematic Reference

Horn Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Horns System Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

1. Command the horns ON and OFF with the scan tool, the P12 horns should turn ON and OFF when changing between the commanded states.

⇒	If the P12 horns are always ON or always OFF, refer to Horns or Horn Command Malfunction.

⇒	If the sound emitted from the P12 horns are not clear and even, refer to Horn - Poor Tone.

2. Observe the scan tool Horn Switch parameter while pressing and releasing the horn pad. The parameter should change from Inactive to Active.

⇒	If the value does not change, refer to Horn Switch Malfunction.

3. Command the horns to sound the predestrian friendly alert function by pressing and releasing the predestrian friendly alert switch. The P12 horns should sound an 8 cycle horn chirp burst each time the switch is pressed.

⇒	If the P12 horns do not perform as specified, refer to Predestrian Friendly Alert Switch Malfunction.

Horns or Horn Command Malfunction

1. Vehicle OFF, disconnect the KR3 horn relay.
2. Test for less than 10 Ω between the ground circuit terminal 6 and ground.

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

3. Vehicle in Service Mode, verify that a test lamp does not illuminates between the control circuit terminal 4 and ground.

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

4. Verify that a test lamp illuminates between the B+ circuit terminal 2 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 B+ circuit fuse is open, test the control circuit terminal 4 for a short to ground.

5. Vehicle OFF, disconnect the harness connector at the P12 horn.
6. Vehicle OFF, test for less than 10 Ω between the ground circuit terminal 1 and ground

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

7. Connect the harness connector at the P12 horn.
8. Vehicle in Service Mode, connect a 15 A fused jumper wire between the B+ circuit terminal 2 and the control circuit terminal 4. Verify the P12 horn is activated.

⇒	If the P12 horn does not activate, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the P12 horn.

9. Connect a test lamp between the control circuit terminal 5 and the B+ circuit terminal 2.
10. Command the Horn Relay 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 ON, test the control circuit for a short to ground. If the circuit tests normal, replace the K9 BCM.

⇒	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 K9 BCM.

11. If all circuits test normal, test or replace the KR3 horn relay.

Horn - Poor Tone

1. Vehicle OFF, disconnect the harness connector at the appropriate P12 horn.
2. Test for less than 1 Ω between the ground circuit terminal 1 and ground.

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

3. Disconnect the KR3 horn relay.
4. Test for less than 1 Ω between the control circuit terminal 4 at the KR3 horn relay and the control circuit terminal 2 at the P12 horn.

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

5. If all circuits test normal, test or replace the P12 horn.

Horn Switch Malfunction

1. Vehicle OFF, disconnect the X2 harness connector at the S33 horn switch.
2. Test for less than 10 Ω between the ground circuit terminal 1 and ground.

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

3. Disconnect the X1 harness connector at the S33 horn switch.
4. Vehicle in Service Mode, test for greater than 10 V between the signal circuit terminal 1 and ground.

⇒	If less than the specified value, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K9 BCM.

5. If all circuits test normal, test or replace the S33 horn switch.

Predestrian Friendly Alert Switch Malfunction

1. Vehicle OFF, disconnect the harness connector at the S78 indicator/multifunction switch.
2. Vehicle in Service Mode, test for greater than 10 V between the signal circuit terminal 3 and ground.

⇒	If less than the specified value, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K9 BCM.

3. If all circuits test normal, test or replace the S78 indicator/multifunction switch.

Horn Test

1. Vehicle OFF, disconnect the harness connector at the appropriate P12 horn.
2. Install a 15 A fused jumper wire between the control terminal 2 and 12 V. Install a jumper wire between the ground terminal 1 and ground. Verify the horn emits a clear and even tone.

⇒	If the sound emitted is not clear and even, replace the P12 horn.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.