FREE REPAIR MANUALS & LABOR GUIDES 1982-2013 Vehicles
Courtesy of Operation CHARM: Car repair manuals for everyone.
Home >> Buick >> 2013 >> Verano L4-2.0L Turbo >> Repair and Diagnosis >> Lighting and Horns >> Horn >> Testing and Inspection >> Horns Malfunction

Horns Malfunction




Horns Malfunction

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.

* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.

Diagnostic Fault Information






Circuit/System Description

The Body Control Module monitors the horn switch signal circuit, when the horn pad is pressed, the Body Control Module detects the drop in the horn switch signal circuit and provides a ground for the Horn printed circuit board relay within the underhood fuse block. The underhood fuse block will then provide B+ voltage to the horn control circuit, sounding the horn

Diagnostic Aids

OnStar(R) RemoteLink(TM) applications or "apps" downloads are available to owners of certain mobile devices. Unwanted or inadvertent horn activations have been associated with these applications to which the customer may be unaware. Contact the GM Technical Assistance Center regarding information on a remedy for this situation.

A short to ground in the horn relay control circuit or a short to voltage in the horn control circuit will cause the horn to sound continuously until the horn overheats 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:

* Debris or water in the horn assembly

* Proper horn mounting hardware torque-Refer to Fastener Tightening Specifications Specifications.

* Debris in the joint where the horns attach to the vehicle

* Debris in direct contact with the horn

* Vehicle components vibrating while the horn is sounding

Reference Information

Schematic Reference

Horn Schematics Electrical Diagrams

Connector End View Reference

Component Connector End Views Outside Rearview Mirror - Driver

Description and Operation

Horns System Description and Operation Description and Operation

Electrical Information Reference

* Circuit Testing Circuit Testing

* Connector Repairs Connector Repairs

* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections

* Wiring Repairs Wiring Repairs

Scan Tool Reference

Control Module References Control Module References for scan tool information

Circuit/System Verification

1. Ignition ON.

2. Verify the scan tool Horn Switch parameter changes between Active and Inactive when pressing and releasing the horn pad.

• If the parameter does not change
Refer to Circuit/System Testing - Horn Switch Malfunction.

• If the parameter changes

3. Verify the P13 Horn Assembly turns ON and OFF and emit a clear and even tone when commanding the Horn Relay On and Off with a scan tool.

• If the P13 Horn Assembly does not turn ON and OFF
Refer to Circuit/System Testing - Horns or Horn Command Malfunction.

• If the sound emitted is not clear and even
Refer to Circuit/System Testing - Horn - Poor Tone.

• If the P13 Horn Assembly turns ON and OFF and emit a even and clear tone

4. All OK.

Circuit/System Testing

Horn Switch Malfunction

1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the S33 Horn Switch. It may take up to 2 minutes for all vehicle systems to power down.

2. Test for less than 10 ohms between the ground circuit terminal A and ground.

• If 10 ohms or greater

1. Ignition OFF.

2. Test for less than 2 ohms in the ground circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms, repair the open/high resistance in the ground connection.

• If less than 10 ohms

3. Ignition ON.

4. Verify the scan tool Horn Switch parameter is Inactive.

• If not Inactive

1. Ignition OFF, disconnect the harness connector at the K9 Body Control Module.

2. Test for infinite resistance between the signal circuit terminal B and ground.

• If less than infinite resistance, repair the short to ground on the circuit.

• If infinite resistance, replace the K9 Body Control Module.

• If Inactive

5. Install a 3 A fused jumper wire between the signal circuit terminal B and the ground circuit terminal A.

6. Verify the scan tool Horn Switch parameter is Active.

• If not Active

1. Ignition OFF, remove the jumper wire, disconnect the harness connector at the K9 Body Control Module, ignition ON.

2. Test for less than 1 V between the signal circuit and ground.

• If 1 V or greater, repair the short to voltage on the circuit.

• If less than 1 V

3. Test for less than 2 ohms in the signal circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms, replace the K9 Body Control Module.

• If Active

7. Test or replace the S33 Horn Switch.

Horns or Horn Command Malfunction

1. Ignition OFF, and all vehicle systems OFF. Disconnect the harness connector at the P13 Horn Assembly. It may take up to 2 minutes for all vehicle systems to power down.

2. Test for less than 10 ohms between the ground circuit terminal 1 and ground.

• If 10 ohms or greater

1. Ignition OFF.

2. Test for less than 2 ohms in the ground circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms, repair the open/high resistance in the ground connection.

• If less than 10 ohms

3. Connect a test lamp between the control circuit terminal 2 and ground, ignition ON.

4. Verify the test lamp does not turn ON and OFF when commanding the Horn Relay On and Off with a scan tool.

• If the test lamp turns ON and OFF
Test or replace the P13 Horn Assembly.

• If the test lamp does not turn ON and OFF

5. Ignition OFF, connect the harness connector at the P13 Horn Assembly. Disconnect the X1 harness connector at the X50A Fuse Block-Underhood, ignition ON.

6. Verify the P13 Horn Assembly is not activated.

• If the P13 Horn Assembly is activated

1. Ignition OFF, disconnect the harness connector at the P13 Horn Assembly, ignition ON.

2. Test for less than 1 V between the control circuit terminal 2 and ground.

• If 1 V or greater, repair the short to voltage on the circuit.

• If less than 1 V, test or replace the P13 Horn Assembly.

• If the P13 Horn Assembly is not activated

7. Connect a 15 A fused jumper wire between the control circuit terminal 17 and B+.

8. Verify the P13 Horn Assembly activates.

• If the P13 Horn Assembly does not activate

1. Ignition OFF, remove the jumper wire, disconnect the harness connector at the P13 Horn Assembly, ignition ON.

2. Test for infinite resistance between the control circuit and ground.

• If less than Infinite resistance, repair the short to ground on the circuit.

• If infinite resistance

3. Test for less than 2 ohms in the control circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms, test or replace the P13 Horn Assembly.

• If the P13 Horn Assembly activates

9. Ignition OFF, connect the X1 harness connector at the X50A Fuse Block-Underhood. Disconnect the X5 harness connector at the K9 Body Control Module, ignition ON.

10. Verify the P13 Horn Assembly is not activated.

• If the P13 Horn Assembly is activated

1. Ignition OFF, disconnect the X2 harness connector at the X50A Fuse Block-Underhood.

2. Test for infinite resistance between the X50A Fuse Block-Underhood control circuit terminal 25 and ground.

• If less than Infinite resistance, repair the short to ground on the circuit.

• If infinite resistance, test or replace the X50A Fuse Block-Underhood.

• If the P13 Horn Assembly is not activated

11. Connect a 3 A fused jumper wire between the control circuit terminal 19 and ground.

12. Verify the P13 Horn Assembly activates.

• If the P13 Horn Assembly does not activate

1. Ignition OFF, remove the jumper wire, disconnect the X2 harness connector at the X50A Fuse Block-Underhood, ignition ON.

2. Test for less than 1 V between the X50A Fuse Block-Underhood control circuit terminal 25 and ground.

• If 1 V or greater, repair the short to voltage on the circuit.

• If less than 1 V

3. Test for less than 2 ohms in the control circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms, test or replace the X50A Fuse Block-Underhood.

• If the P13 Horn Assembly activates

13. Replace the K9 Body Control Module.

Horn - Poor Tone

1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the P13 Horn Assembly. It may take up to 2 minutes for all vehicle systems to power down.

2. Test for less than 10 ohms between the ground circuit terminal 1 and ground.

• If 10 ohms or greater

1. Ignition OFF.

2. Test for less than 2 ohms in the ground circuit end to end.

• If 2 ohms or greater, repair the high resistance in the circuit.

• If less than 2 ohms, repair high resistance in the ground connection.

• If less than 10 ohms

3. Ignition OFF, disconnect the X1 harness connector at the X50A Fuse Block-Underhood.

4. Test for less than 2 ohms between the P13 Horn Assembly control circuit terminal 2 and the X50A Fuse Block-Underhood control circuit terminal 17 X1.

• If 2 ohms or greater
Repair the high resistance in the control circuit.

• If less than 2 ohms

5. Test or replace the P13 Horn Assembly.

Component Testing

Horn Test

1. Ignition OFF, disconnect the harness connector at the 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.

3. Verify the P12 Horn turns ON and OFF

• If the P12 Horn does not turn ON and OFF
Replace the P12 Horn.

• If the P12 Horn turns ON and OFF

4. All OK

Horn Switch

1. Ignition OFF, disconnect the harness connector at the S33 Horn Switch.

2. Test for infinite resistance between the signal terminal B and the ground terminal A with the switch in the open position.

• If less than infinite resistance
Replace the S33 Horn Switch.

• If infinite resistance

3. Test for less than 3 ohms between the signal terminal B and the ground terminal A with the switch in the closed position.

• If 3 ohms or greater
Replace the S33 Horn Switch.

• If less than 3 ohms

4. All OK

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests after completing the repair.

* Steering Wheel Horn Contact Replacement Service and Repair

* Fuse Block Replacement Fuse Block Replacement

* Horn Replacement Service and Repair

* Control Module References Control Module References for Body Control Module replacement, setup and programming

pro multis Credits:Operation CHARM About Operation CHARM