Test Description
The numbers below refer to the step numbers on the diagnostic table.
- 4: This step tests if ground is constantly being applied to the horn relay.
- 5: The horn relay control circuit includes the horn switch. The horn switch is part of the inflatable restraint steering wheel module. The horn switch must be tested for a short to ground when testing the relay control circuit.
| Step | Action | Yes | No |
|---|---|---|---|
| 1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
| 2 | Install a scan tool. Turn ON the ignition, with the engine OFF. With a scan tool, command the body control module (BCM) Horn Output ON and OFF. Are the horns ON at all times? | Go to Step 3 | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems |
| 3 | Turn OFF the ignition. Disconnect the horn relay. Are the horns ON at all times? | Go to Step 8 | Go to Step 4 |
| 4 | Connect a test lamp between the battery positive voltage circuit of the horn relay coil and the horn relay control circuit. Does the test lamp illuminate? | Go to Step 5 | Go to Step 6 |
| 5 | IMPORTANT: The horn switch is part of the inflatable restraint steering wheel module. Refer to Inflatable Restraint Steering Wheel Module Replacement in SIR. To disable the SIR system, refer to SIR Disabling and Enabling Zone 3 in SIR.Test the horn relay control circuit for a short to ground. The horn relay control circuit includes the horn switch. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.Did you find and correct the condition? | Go to Step 11 | Go to Step 7 |
| 6 | Inspect for poor connections at the horn relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 11 | Go to Step 9 |
| 7 | Inspect for poor connections at the harness connector of the BCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 11 | Go to Step 10 |
| 8 | Repair the short to voltage in the horn control circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 11 | |
| 9 | Replace the horn relay. Refer to Relay Replacement (Within an Electrical Center) or Relay Replacement (Attached to Wire Harness) . Did you complete the replacement? | Go to Step 11 | |
| 10 | Replace the BCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | Go to Step 11 | |
| 11 | Operate the horns. Do the horns operate properly? | System OK | Go to Step 1 |
| IMPORTANT |
|---|
| The horn switch is part of the inflatable restraint steering wheel module. Refer to Inflatable Restraint Steering Wheel Module Replacement in SIR. |
Horns Always On
The numbers below refer to the step numbers on the diagnostic table.
- 4: Verifies that the body control module (BCM) is providing ground to the horn relay.
- 5: Tests for voltage at the battery positive voltage terminal of the horn relay coil.
- 7: Tests for voltage at the battery positive voltage terminal of the horn relay switch. The HORN fuse supplies power to the battery positive voltage terminal of the horn relay switch.
- 15: The horns need maximum current flow to operate properly. A high resistance (greater than 0.5 ohms) in the horn control circuit or the horn ground circuit could cause operating problems with the horns. Check the circuits for faults that would restrict current flow.
- 17: The horn relay control circuit includes the horn switch. The horn switch is part of the inflatable restraint steering wheel module. The horn switch must be tested for a high resistance, an open or a short to voltage when testing the relay control circuit.
| Step | Action | Yes | No |
|---|---|---|---|
| 1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
| 2 | Depress the horn switch. Do the horns operate? | Go to Step 3 | Go to Step 5 |
| 3 | Install a scan tool. Turn ON the ignition, with the engine OFF. With a scan tool, command the body control module (BCM) Horn Output ON and OFF. Do the horns operate? | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 4 |
| 4 | Test the BCM portion of the horn relay control circuit for a high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 24 | Go to Step 13 |
| 5 | Turn OFF the ignition. Disconnect the horn relay. Connect a test lamp between the battery positive voltage circuit of the horn relay coil and a good ground. Does the test lamp illuminate? | Go to Step 6 | Go to Step 16 |
| 6 | Connect a test lamp between the battery positive voltage circuit of the horn relay coil and the horn relay control circuit. Depress and hold the horn switch. Does the test lamp illuminate? | Go to Step 7 | Go to Step 17 |
| 7 | Connect a test lamp between the battery positive voltage circuit of the horn relay switch and a good ground. Does the test lamp illuminate? | Go to Step 8 | Go to Step 18 |
| 8 | Momentarily connect a 15-amp fused jumper wire between the battery positive voltage circuit of the horn relay switch and the horn control circuit. Do the horns operate? | Go to Step 14 | Go to Step 9 |
| 9 | Reconnect the horn relay. Disconnect the horn connector. Connect a test lamp between the horn control circuit and a good ground. Depress and hold the horn switch. Does the test lamp illuminate? | Go to Step 10 | Go to Step 19 |
| 10 | Connect a test lamp between the horn control circuit and the horn ground circuit. Depress and hold the horn switch. Does the test lamp illuminate? | Go to Step 11 | Go to Step 20 |
| 11 | Inspect for poor connections at the harness connector of the horn. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 24 | Go to Step 12 |
| 12 | Connect a 15-amp fused jumper wire between the positive battery terminal and the control terminal of the horn. Connect another jumper wire between the negative battery terminal and the ground terminal of the horn. Do the horns operate? | Go to Step 15 | Go to Step 23 |
| 13 | Inspect for poor connections at the harness connector of the BCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 24 | Go to Step 21 |
| 14 | Inspect for poor connections at the horn relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 24 | Go to Step 22 |
| 15 | Repair the high resistance in the horn control circuit or the horn ground circuit. Refer to Circuit Testing , and to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 24 | |
| 16 | Repair the open or high resistance in the battery positive voltage circuit of the horn relay coil. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 24 | |
| 17 | IMPORTANT: The horn switch is part of the inflatable restraint steering wheel module. Refer to Inflatable Restraint Steering Wheel Module Replacement in SIR. To disable the SIR system refer to SIR Disabling and Enabling Zone 3 in SIR.Repair the open or short to voltage in the horn relay control circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.Did you complete the repair? | Go to Step 24 | |
| 18 | Repair the open or high resistance in the battery positive voltage circuit of the horn relay switch. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 24 | |
| 19 | Repair the open or high resistance in the horn control circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 24 | |
| 20 | Repair the open or high resistance in the horn ground circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 24 | |
| 21 | Replace the BCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the repair? | Go to Step 24 | |
| 22 | Replace the horn relay. Refer to Relay Replacement (Within an Electrical Center) or Relay Replacement (Attached to Wire Harness) . Did you complete the replacement? | Go to Step 24 | |
| 23 | Replace the horns. Refer to Horn Replacement . Did you complete the replacement? | Go to Step 24 | |
| 24 | Operate the horns. Do the horns operate properly? | System OK | Go to Step 1 |
| IMPORTANT |
|---|
| The horn switch is part of the inflatable restraint steering wheel module. Refer to Inflatable Restraint Steering Wheel Module Replacement in SIR. |
Horns Inoperative
Horns - Poor Tone
| Step | Action | Yes | No |
|---|---|---|---|
| 1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
| 2 | Depress the horn switch. Do the horns have a harsh tone or buzzing? | Go to Step 3 | Go to Symptoms - Horns |
| 3 | Test the horn mounting hardware for adequate torque. The hardware should be tightened to 10 N.m (7 lb ft). Inspect the horns for debris in the joint where the horns attach to the vehicle. Did you find and correct the condition? | Go to Step 7 | Go to Step 4 |
| 4 | Disconnect the horn connector. Connect a 15-amp fuse jumper wire between the positive battery terminal and the control terminal of the horn. Connect another jumper wire between the negative battery terminal and the ground terminal of the horn. Do the horns have a harsh tone or buzzing? | Go to Step 6 | Go to Step 5 |
| 5 | Repair the high resistance in the horn control circuit or the horn ground circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 7 | |
| 6 | Replace the horns. Refer to Horn Replacement . Did you complete the replacement? | Go to Step 7 | |
| 7 | Operate the horns. Do the horns operate properly? | System OK | Go to Step 1 |
Horns - Poor Tone
System Description
The horn system consists of the following components
- The BATTERY fuse
- The HORN fuse
- The horn relay
- The horn switch
- The horns
- The body control module (BCM)
System Operation
The vehicle horn system is activated under the following conditions
- The horn switch is depressed.
- The body control module (BCM) commands the horns on. The BCM commands the horns on under any of the following conditions: When the content theft deterrent system detects a vehicle intrusion. For further information refer to «Content Theft Deterrent (CTD) Description and Operation»(ref-200381-S06501802372005102000000) in Theft Deterrent. When the panic button is depressed on the remote control door lock transmitter. For further information refer to «Keyless Entry System Description and Operation»(ref-200378-S09866112732005102000000) in Keyless Entry. When the lock button on the keyless entry transmitter is pressed twice within 5 seconds, a horn chirp will sound to notify the driver that the vehicle has been locked. For further information refer to «Keyless Entry System Description and Operation»(ref-200378-S09866112732005102000000) in Keyless Entry.
Circuit Operation
Battery positive voltage is applied at all times to the horn relay coil and the horn relay switch. Pressing the horn switch applies ground to the horn relay control circuit. The BCM may also apply ground to the horn relay control circuit as described above. When the horn relay control circuit is grounded, the horn relay is energized and battery positive voltage is applied to the horns through the horn control circuit. The horns sound as long as ground is applied to the horn relay control circuit.