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Horn System Cadillac DTS I

Horns 2 illustrations ~2026 words

Fastener Tightening Specifications

ApplicationSpecification
MetricEnglish
Horn and Bracket Assembly to the Body15 N.m11 lb ft
Steering Wheel Horn Switch Bolts7 N.m62 in lb
Steering Wheel Switch Screws5 N.m44 in lb

Scheme 1

Scheme 1: Horn Schematics
Scheme 1: Horn Schematics

DIAGNOSTIC CODE INDEX

DTCDescription
DTC B2750B2750 00: Horn Relay Coil Circuit

DIAGNOSTIC CODE INDEX

Diagnostic Starting Point - Horns

Begin the system diagnosis with the Diagnostic System Check - Vehicle . 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.

Diagnostic Instructions

  1. Perform the «Diagnostic System Check - Vehicle»(/cadillac/dts/i-2005-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/cadillac/dts/i-2005-2011/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/cadillac/dts/i-2005-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Diagnostic Fault Information

CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Horn Relay ControlB2750 00B2750 00B2750 00
Horn Control221
Horn Switch Ground22
Horn Ground22
1. Horn Always ON 2. Horn Inoperative

Circuit/System Description

The body control module (BCM) controls the HORN relay by grounding the control circuit of the horn relay coil energizing the relay. When the HORN relay is energized, the horn relay contacts close applying voltage through the HORN fuse and the horn control circuit to the horns.

Conditions for Running the DTC

When the output is actively being requested by the BCM.

Conditions for Setting the DTC

The BCM detects a short to ground, open, or short to voltage in the horn relay control circuit for approximately 125 milliseconds.

Action Taken When the DTC Sets

The BCM disables the output to the HORN relay until the next ignition cycle.

Conditions for Clearing the DTC

  1. The DTC clears when the fault is no longer detected.
  2. The current DTC will become history when the request for the output is removed.
  3. The history DTC will clear after 50 consecutive fault-free ignition cycles have occurred.

Reference Information

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__circuit-testing)
  2. «Connector Repairs»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__testing-for-intermittent-conditions-poor)
  4. «Wiring Repairs»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

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

Circuit/System Testing

  1. Ignition OFF, disconnect the X2 harness connector at the underhood fuse block.
  2. Connect a test lamp between B+ and the control circuit terminal 26.
  3. Ignition ON, command the horn 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 OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM. If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the BCM.
  4. If all circuits test normal, replace the underhood fuse block.

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Underhood Electrical Center or Junction Block Replacement»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-introduction)
  2. «Control Module References»(/cadillac/dts/i-2005-2011/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for BCM replacement, setup and programming

Symptoms - Horns

IMPORTANTThe following steps must be completed before using the symptom tables: Perform Diagnostic System Check - Vehicle , 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 Review the system operation in order to familiarize yourself with the system functions. Refer to Horns System Description and Operation .

Visual/Physical Inspection

  1. Inspect for aftermarket devices which could affect the operation of the horn system. Refer to «Checking Aftermarket Accessories»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__checking-aftermarket-accessories) .
  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 .

Symptom List

Refer to a symptom diagnostic procedure Horns Malfunction in order to diagnose the symptom.

  1. Perform the «Diagnostic System Check - Vehicle»(/cadillac/dts/i-2005-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/cadillac/dts/i-2005-2011/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/cadillac/dts/i-2005-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Horn Relay ControlB2750 00B2750 00B2750 00
Horn Control221
Horn Switch Ground22
Horn Ground22
1. Horn Always On 2. Horn Inoperative

Battery positive voltage is applied at all times to the horn relay coil and the horn relay switch. Pressing the horn switch applies ground through the switch contacts and the horn relay control circuit to the coil side of the relay, energizing 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 ground to the horn relay control circuit as described above. The horns sound as long as ground is applied to the horn relay control circuit.

Diagnostic Aids

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

  1. Debris or water in the horn assembly
  2. Proper horn mounting hardware torque-Refer to «Fastener Tightening Specifications»(/cadillac/dts/i-2005-2011/remont/horns/#horn-system__fastener-tightening-specifications) .
  3. Debris in the joint where the horns attach to the vehicle

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__circuit-testing)
  2. «Connector Repairs»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__testing-for-intermittent-conditions-poor)
  4. «Wiring Repairs»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Ignition OFF, connect a test lamp between the horn fuse test point and ground.
  2. Press and release the horn switch. The test lamp should turn ON and OFF when changing between the commanded states. If the test lamp does not illuminate or remains illuminated at all times, refer to «Horn Switch Circuit Test»(/cadillac/dts/i-2005-2011/remont/horns/#horn-system) .
  3. Ignition ON, command the horn 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 does not illuminate, test the control circuit terminal 18 at the BCM for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.
  4. Connect a 15A fused jumper wire between the horn fuse test point and B+. The horn should sound and emit a clear and even tone. If the horn does not sound, refer to «Horn Circuit Test»(/cadillac/dts/i-2005-2011/remont/horns/#horn-system) . If the sound emitted is not clear and even, refer to «Horn - Poor Tone»(/cadillac/dts/i-2005-2011/remont/horns/#horn-system) .

Horn Switch Circuit Test

  1. Ignition OFF, disconnect the harness connector at the horn switch.
  2. Test for less than 1 ohm between the ground circuit terminal 2 and ground. If greater than the specified range, test the ground circuit for and open/high resistance.
  3. Connect the harness connector at the horn switch. Disconnect the X2 harness connector at the underhood fuse block.
  4. Connect a test lamp between B+ and the control circuit terminal 26.
  5. Press and release the horn switch. 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 or a sticking horn switch. If the circuit tests normal, replace the BCM. If the test lamp is always OFF, test the control circuit for a short to voltage, an open high resistance, or a horn switch which is not closing.
  6. Connect the harness connector at the underhood fuse block. Disconnect the harness connector at the horn assembly.
  7. Verify that a test lamp does not illuminate between the control circuit terminal B and ground. If the test lamp illuminates, test the control circuit for a short to voltage. If the circuit tests normal, replace the underhood fuse block.
  8. If all circuits test normal, replace the underhood fuse block.

Horn Circuit Test

  1. Ignition OFF, disconnect the harness connector at the horn assembly.
  2. Test for less than 1 ohm between the ground circuit terminal A and ground. If greater than the specified range, test the ground circuit for and open/high resistance.
  3. Connect a test lamp between the control circuit terminal B and ground.
  4. Press and release the horn switch. 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 voltage. If the circuit tests normal, replace the underhood fuse block. If the test lamp is always OFF and the HORN fuse is good, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the underhood fuse block. If the test lamp is always OFF and the HORN fuse is open, test the control circuit for a short to ground. If the circuit tests normal, test or replace the horn assembly.
  5. If all circuit test normal, test or replace the horn assembly.

Horn - Poor Tone

  1. Ignition OFF, disconnect the harness connector at the horn assembly.
  2. Test for less than 1 ohm between the horn assembly ground circuit terminal A and ground. If greater than the specified range, test the ground circuit for a high resistance.
  3. Disconnect the X1 harness connector at the underhood fuse block.
  4. Test for less than 1 ohm between the control circuit terminal 9 at the underhood fuse block and the control circuit terminal B at the horn assembly. If greater than the specified range, test the control circuit for a high resistance.
  5. If all circuits test normal, test or replace the horn assembly.

Component Testing

Horn

  1. Ignition OFF, disconnect the harness connector at the horn assembly.
  2. Install a 15A fused jumper wire between the control terminal B and 12 volts. Install a jumper wire between the ground terminal A and ground. Verify the horn emits a clear and even tone. If the sound emitted is not clear and even, replace the horn assembly.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Horn Replacement»(/cadillac/dts/i-2005-2011/remont/horns/#horn-system)
  2. «Horn Switch Replacement»(/cadillac/dts/i-2005-2011/remont/horns/#horn-system)
  3. «Control Module References»(/cadillac/dts/i-2005-2011/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for BCM replacement, setup, and programming

Removal Procedure

  1. Raise and support the vehicle. Refer to «Lifting and Jacking the Vehicle»(/cadillac/dts/i-2005-2011/remont/hoistjack/#general-information__lifting-jacking-the-vehicle) .
  2. Remove the lower air deflector. Refer to «Front Air Deflector Replacement»(/cadillac/dts/i-2005-2011/remont/exterior-body-panels/#bumper-system-fascia) .
  3. Disconnect the horn connectors (1) from the horns.
  4. Remove the fastener securing the horns to the body.
  5. Remove the horns from the body.

Installation Procedure

  1. Install the horns to the body.
  2. Install the fastener in order to secure the horns to the body. Tighten: Tighten the bolts to 15 N.m (11 lb ft).
  3. Connect the horn connectors (1) to the horns.
  4. Install the front air deflector. Refer to «Front Air Deflector Replacement»(/cadillac/dts/i-2005-2011/remont/exterior-body-panels/#bumper-system-fascia) .
  5. Lower the vehicle.

Scheme 2

Scheme 2: Horn Switch Replacement
Scheme 2: Horn Switch Replacement
CalloutComponent Name
NOTE: Refer to Fastener Notice . Fastener Tightening Specifications: Refer to Fastener Tightening Specifications . Preliminary Procedure: Remove the inflatable restraint steering wheel module. Refer to Inflatable Restraint Steering Wheel Module Replacement .
1Steering Wheel Horn Switch Bolts (Qty: 4) Tip: Hand start the bolts on installation to avoid cross threading. Tighten: 7 N.m (62 lb in)
2Steering Wheel Horn Switch Washers (Qty: 4)
3Steering Wheel Horn Switch Screws (Qty: 2) Tip: Hand start the screws on installation to avoid cross threading. Tighten: 5 N.m (44 lb in)
4Steering Wheel Horn Switch Assembly Tip: Disconnect the horn switch electrical.
NOTE
Refer to Fastener Notice .

System Description

The horn system consists of the following components

  1. HORN fuse
  2. Horn PCB relay
  3. Horn switch
  4. Horn
  5. Body control module (BCM)

System Operation

  1. The vehicle horns are activated whenever the horn switch is depressed.
  2. 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»(/cadillac/dts/i-2005-2011/remont/door-locks-anti-theft-systems/#keyless-entry-system-remote-functions__keyless-entry-system-description-operation) . When the content theft deterrent system detects a vehicle intrusion. For further information refer to «Content Theft Deterrent (CTD) Description and Operation»(/cadillac/dts/i-2005-2011/remont/door-locks-anti-theft-systems/#theft-deterrent-system__content-theft-deterrent-ctd-description) . 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»(/cadillac/dts/i-2005-2011/remont/door-locks-anti-theft-systems/#keyless-entry-system-remote-functions__keyless-entry-system-description-operation) .

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. When the horn relay control circuit is grounded, the horn relay is energized and battery positive voltage is applied to the horn through the horn control circuit. The horn will sound as long as ground is applied to the horn relay control circuit.