Horns Schematic Icons
Horns Schematic Icons Icon Icon Definition CAUTION: When performing service on or near the SIR components or the SIR wiring, the SIR system must be disabled. Refer to SIR Disabling and Enabling Zones. Failure to observe the correct procedure could cause deployment of the SIR components, personal injury, or unnecessary SIR system repairs
Scheme 1
Scheme 2
| Callout | Component Name |
|---|---|
| 1 | Horn - Low Note |
| 2 | Horn - High Note |
| 3 | Horn Assembly Connector |
| 4 | Steering Wheel (LHD shown, RHD similar) |
| 5 | Horn Switch (Part of Inflatable Restraint Steering Wheel Module) |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
- 4: Tests if ground is constantly being applied to the horn relay.
- 5: The horn relay control circuit includes the horn slip ring and the horn switch. The horn slip ring and horn switch must be tested for a short to ground when testing the relay control circuit. Refer to «Circuit Testing»(ref-197533-S09080459212005101200000) and «Wiring Repairs»(ref-197533-S00106490252005101200000) in Wiring Systems.
| 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 dash integration module (DIM) 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 | Test the horn relay control circuit for a short to ground. The horn relay control circuit includes the horn slip ring and 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 DIM. 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. Did you complete the replacement? | Go to Step 11 | |
| 10 | Replace the DIM. 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 |
Horns Always On
The numbers below refer to the step numbers on the diagnostic table.
- 4: Verifies that the dash integration module (DIM) 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 SEATS circuit breaker supplies power to the battery positive voltage terminal of the horn relay switch.
- 13: The horns need maximum current flow to operate properly. A high resistance, greater than 0.5 ohm, in the horn control circuit or the horn ground circuit could cause operating problems with the horns. Inspect the circuits for faults that would restrict current flow.
- 15: The horn relay control circuit includes the horn slip ring and the horn switch. The horn slip ring and horn switch must be tested for a high resistance, an open or a short to voltage when testing the relay control circuit. Refer to «Circuit Testing»(ref-197533-S09080459212005101200000) and «Wiring Repairs»(ref-197533-S00106490252005101200000) in Wiring Systems.
| 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 dash integration module (DIM) 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 21 | Go to Step 11 |
| 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 14 |
| 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 15 |
| 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 16 |
| 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 12 | Go to Step 9 |
| 9 | Reconnect the horn relay. Disconnect either 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 17 |
| 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 13 | Go to Step 18 |
| 11 | Inspect for poor connections at the harness connector of the DIM. 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 21 | Go to Step 19 |
| 12 | 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 21 | Go to Step 20 |
| 13 | Repair the high resistance in the horn control circuit or the horn ground circuit. A resistance as low as 0.5 ohm could cause operating problems with the horns. Also, though unlikely, it is possible that both horns are defective. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 21 | |
| 14 | 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 21 | |
| 15 | Repair the open or short to voltage in the horn relay control circuit. The horn relay control circuit includes the horn slip ring and the horn switch. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 21 | |
| 16 | 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 21 | |
| 17 | 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 21 | |
| 18 | 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 21 | |
| 19 | Replace the DIM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the repair? | Go to Step 21 | |
| 20 | Replace the horn relay. Did you complete the replacement? | Go to Step 21 | |
| 21 | Operate the horns. Do the horns operate properly? | System OK | Go to Step 1 |
Horns Inoperative
The number below refers to the step number on the diagnostic table.
- 9: 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. Inspect the circuits for faults that would restrict current flow.
| Step | Action | Yes | No |
|---|---|---|---|
| DEFINITION: This diagnostic procedure is for use with systems that have multiple horns in which one of the horns is inoperative. | |||
| 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 all of the horns operate? | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 3 |
| 3 | Disconnect the inoperative horn. 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 4 | Go to Step 7 |
| 4 | 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 5 | Go to Step 8 |
| 5 | Inspect for poor connections at the inoperative 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 11 | Go to Step 6 |
| 6 | 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. Does the horn sound? | Go to Step 9 | Go to Step 10 |
| 7 | Repair the open or poor connection in the horn control circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 11 | |
| 8 | Repair the open or poor connection in the horn ground circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 11 | |
| 9 | Repair the high resistance in the horn control circuit or the horn ground circuit of the horn. A resistance as low as 0.5 ohms could cause operating problems with the horn. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 11 | |
| 10 | Replace the inoperative horn. Refer to Horn Replacement . Did you complete the replacement? | Go to Step 11 | |
| 11 | Operate the horns. Do the horns operate properly? | System OK | Go to Step 1 |
Horns Inoperative - One Horn
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. Refer to Fastener Tightening Specifications . 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 | Perform the following for each of the horns: 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. Does the horn 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 horn. 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
- HORN fuse
- RADIO fuse
- Horn relay
- Inflatable restraint steering wheel coil
- Horn switch
- Horns
- Body control module (BCM)
- Steering wheel radio control switch
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-197565-S29438557032005101200000) in Theft Deterrent. When the keyless entry system is used to lock the vehicle, a horn chirp may sound to notify the driver that the vehicle has been locked. The notification feature may be enabled or disabled through personalization. For further information refer to «Keyless Entry System Description and Operation»(ref-197557-S17508693412005101200000) in Keyless Entry. When the OnStar® system is used to sound the horns if equipped. For further information, refer to «OnStar Description and Operation»(ref-197531-S06544126662005101200000) in Cellular Communications.
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.