Horn System Buick LaCrosse I

Fastener Tightening Specifications

Fastener Tightening Specifications

Scheme 1

Scheme 2

Scheme 3

Horns Connector End Views

Horn Assembly Connector Part Information OEM: 15419715 Service: See Catalog 2-Way F GT 150 Series Sealed (GY) Pin Wire Color Circuit No. Function A BK 1250 Ground B D-GN 29 Horn Control

DIAGNOSTIC CODE INDEX

DIAGNOSTIC CODE INDEX

Diagnostic Starting Point - Horns

Begin the system diagnosis with the Diagnostic System Check - Vehicle in Vehicle DTC Information. The Diagnostic System Check will provide the following information

1. The identification of the control modules which command the system
2. The ability of the control modules to communicate through the serial data circuit
3. The identification of any stored diagnostic trouble codes (DTCs) and their status

The use of the Diagnostic System Check will identify the correct procedure for diagnosing the system and where the procedure is located.

Scan Tool Output Controls

Scan Tool Output Controls

Scan Tool Data List

The Horns Scan Tool Data List contains all of the horn related parameters that are available on the scan tool. The parameters in the list are arranged in alphabetical order. The column, Data List, indicates the location of the parameter within the scan tool menu selections. Use the Horns Scan Tool Data List as directed by a diagnostic table or in order to supplement the diagnostic procedures. Begin all of the diagnostic procedures with Diagnostic System Check - Vehicle in Vehicle DTC Information.

Use the Scan Tool Data List only after the following is determined

1. There is no published DTC procedure nor published symptom procedure for the customer concern.
2. The DTC or symptom diagnostic procedure indicated by the diagnostic system check does not resolve the customer concern.

The Typical Data Values are obtained from a properly operating vehicle under the conditions specified in the first row of the Scan Tool Data List table. Comparison of the parameter values from the suspect vehicle with the Typical Data Values may reveal the source of the customer concern.

Scan Tool Data List

Circuit Description

The vehicle horns are activated whenever ground is applied to the horn relay coil through the horn relay control circuit. Ground may be applied by either of the following

1. The body control module (BCM)
2. The horn switch

DTC Descriptor

This diagnostic procedure supports the following DTC

DTC B2752 Horn Relay Coil Circuit Low

Conditions for Running the DTC

1. The body control system voltage must be between 9-16 volts.
2. The BCM is not commanding the horn relay to energize.

Conditions for Setting the DTC

The BCM detects a short to ground or an open in the horn relay control circuit for approximately 300 milliseconds.

Action Taken When the DTC Sets

1. If the horn relay control circuit is shorted to ground, the horns will remain ON at all times.
2. The BCM stores DTC B2752 in memory.

Conditions for Clearing the DTC

1. A current DTC will clear when the fault is no longer present and the ignition switch is cycled.
2. A history DTC will clear after 100 consecutive ignition cycles without a fault present.
3. A scan tool may be used to clear history and current DTCs.

Diagnostic Aids

1. Always begin diagnosis with the first DTC listed on the scan tool.
2. The scan tool must display DTC B2752 as a current code before performing these diagnostics.
3. Inspect for a sticking horn pad and or switch.
4. Perform a visual inspection for loose or poor connections at all related components. Refer to «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing) in Wiring Systems.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. 2: Listen for an audible click when the horn relay operates. Command both the ON and OFF states. Repeat the commands as necessary.
2. 3: This step tests for voltage at the coil side of the horn relay. The HORN fuse supplies power to the coil side of the horn relay.
3. 4: This step verifies that the BCM is providing ground to the horn relay.
4. 5: This step tests if ground is constantly being applied to the horn relay.

DTC B2752

The vehicle horns are activated whenever ground is applied to the horn relay coil through the horn relay control circuit. Ground may be applied by either of the following

1. The body control module (BCM)
2. The horn switch

This diagnostic procedure supports the following DTC

DTC B2753 Horn Relay Coil Circuit High

1. The body control system voltage must be between 9-16 volts.
2. The BCM is commanding the horn relay to energize.

The BCM detects a short to voltage in the horn relay control circuit for approximately 300 milliseconds.

1. The horns are inoperative from the BCM and the horn switch.
2. The BCM stores DTC B2753 in memory.

1. A current DTC will clear when the fault is no longer present and the ignition switch is cycled.
2. A history DTC will clear after 100 consecutive ignition cycles without a fault present.
3. A scan tool may be used to clear history and current DTCs.

1. Always begin diagnosis with the first DTC listed on the scan tool.
2. The scan tool must display DTC B2753 as a current code before performing these diagnostics.

The numbers below refer to the step numbers on the diagnostic table.

1. 2: Listen for an audible click when the horn relay operates. Command both the ON and OFF states. Repeat the commands as necessary.
2. 3: This step tests for voltage at the coil side of the horn relay. The HORN fuse supplies power to the coil side of the horn relay.
3. 4: This step verifies that the BCM is providing ground to the horn relay.
4. 5: This step tests if ground is constantly being applied to the horn relay.

DTC B2753

Symptoms - Horns

1. Perform «Diagnostic System Check - Vehicle»(/buick/lacrosse/i-2004-2009/remont/oem-general-information/#vehicle-dtc-information) in Vehicle DTC Information, before using the symptom tables in order to verify that all of the following are true: There are no DTCs set. The control modules can communicate via the serial data link.
2. Review the system operation in order to familiarize yourself with the system functions. Refer to «Horns System Description and Operation»(/buick/lacrosse/i-2004-2009/remont/horns/#horn-system) .

Visual/Physical Inspection

1. Inspect for aftermarket devices which could affect the operation of the horn system. Refer to «Checking Aftermarket Accessories»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__checking-aftermarket-accessories) in Wiring Systems.
2. Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.
3. Perform the following if a horn buzzes or has a harsh tone: Inspect for debris in the joint where the horn fastens to the vehicle. Test the torque of the horn mounting hardware. The horn mounting hardware should be tightened to a torque of 10 N.m (7 lb ft).

Intermittent

Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Symptom List

Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom

1. «Horns Always On»(/buick/lacrosse/i-2004-2009/remont/horns/#horn-system)
2. «Horns Inoperative»(/buick/lacrosse/i-2004-2009/remont/horns/#horn-system)
3. «Horns - Poor Tone»(/buick/lacrosse/i-2004-2009/remont/horns/#horn-system__horns-poor-tone)

The number below refers to the step number on the diagnostic table.

1. 7: Tests if ground is constantly being applied to the horn relay.

Horns Always On

The numbers below refer to the step numbers on the diagnostic table.

1. 4: This step verifies that the body control module (BCM) is providing ground to the horn relay.
2. 5: This step tests for voltage at the battery positive voltage terminal of the horn relay coil.
3. 7: This step 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.
4. 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.
5. 17: The horn relay control circuit includes the horn slip ring and the horn switch. The horn switch is part of the inflatable restraint steering wheel module. The horn slip ring and the 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»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__circuit-testing) and «Wiring Repairs»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__wiring-repairs) in Wiring Systems and «Inflatable Restraint Steering Wheel Module Replacement»(/buick/lacrosse/i-2004-2009/remont/airbag/#supplemental-inflatable-restraint-system) in SIR.

Horns Inoperative

Horns - Poor Tone

Horns - Poor Tone

Removal Procedure

1. Open the hood.
2. Remove the RH headlamp assembly. Refer to «Headlamp, Fog Lamp, Turn Signal Lamp, Side Marker Lamp Replacement - Front»(/buick/lacrosse/i-2004-2009/remont/exterior-lights/#lighting-systems) in Lighting Systems.
3. Disconnect the horn electrical connector.
4. Remove the horn bracket bolt.
5. Remove the horn from the frame rail extension.

Installation Procedure

1. Position the horn assembly to the frame rail extension. Insert the horn anti-rotation tab into the slot on the frame rail.
2. Install the horn bracket bolt. Tighten: Tighten the bolt to 15 N.m (11 lb ft).
3. Connect the horn electrical connector.
4. Install the RH headlamp assembly. Refer to «Headlamp, Fog Lamp, Turn Signal Lamp, Side Marker Lamp Replacement - Front»(/buick/lacrosse/i-2004-2009/remont/exterior-lights/#lighting-systems) in Lighting Systems.
5. Close the hood.

System Description

The horn system consists of the following components

1. HORN fuse
2. Horn relay
3. Horn slip ring
4. Horn switch (The horn switch is part of the inflatable restraint steering wheel module.)
5. Horn assembly
6. Body Control Module (BCM)

System Operation

The vehicle horn system is activated under the following conditions

1. The horn switch is depressed.
2. The body control module (BCM) commands the horns on. The BCM commands the horns on under any of the following conditions: When the panic button is depressed on the remote control door lock transmitter. For further information refer to «Keyless Entry System Description and Operation»(/buick/lacrosse/i-2004-2009/remont/door-locks-anti-theft-systems/#keyless-entry-system) in Keyless Entry. 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»(/buick/lacrosse/i-2004-2009/remont/door-locks-anti-theft-systems/#keyless-entry-system) 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.

See also:
• Diagnostic System Check - Vehicle
• Testing for Intermittent Conditions and Poor Connections
• Circuit Testing
• Wiring Repairs
• Connector Repairs
• Control Module References
• Checking Aftermarket Accessories
• Inflatable Restraint Steering Wheel Module Replacement
• Headlamp, Fog Lamp, Turn Signal Lamp, Side Marker Lamp Replacement - Front
• FASTENER NOTICE
• Keyless Entry System Description and Operation
• DTC B2752
• Diagnostic Aids
• Horns - Poor Tone
• Symptoms - Horns