Home ReviewsRefund
Home/Chevrolet/Express G2500/Chevrolet Express G2500 (2013-2013)/Repair manual/Horns/Horn System
Contents Wiring diagrams Section: Horns All sections

Horn System Chevrolet Express G2500

Horns 1 illustration ~2138 words

Fastener Tightening Specifications

ApplicationSpecification
MetricEnglish
Horn Mounting Bracket to Radiator Support Nut25 N.m18 lb ft

Fastener Tightening Specifications

Scheme 1

Scheme 1: Horn Wiring Schematics
Scheme 1: Horn Wiring Schematics

Diagnostic Code Index

DTCDescription
DTC B2750DTC B2750 00 Horn Relay Coil Circuit

DIAGNOSTIC CODE INDEX

Diagnostic Instructions

  1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/express-g2500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/express-g2500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/express-g2500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__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 horn 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»(/chevrolet/express-g2500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/chevrolet/express-g2500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/express-g2500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  4. «Wiring Repairs»(/chevrolet/express-g2500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__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 X3 harness connector at the underhood fuse block.
  2. Connect a test lamp between the control circuit terminal 49 and B+.
  3. Command the horns 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 Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Body Wiring Harness Junction Block Replacement»(/chevrolet/express-g2500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-repair-instructions)
  2. «Control Module References»(/chevrolet/express-g2500/2013-2013/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»(/chevrolet/express-g2500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__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»(/chevrolet/express-g2500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/express-g2500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/express-g2500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Horn Relay Control21B2750 00
Horn Control221
Horn Switch Ground2
Horn Ground2
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

OnStar® RemoteLink™ 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

  1. Debris or water in the horn assembly.
  2. Proper horn mounting hardware torque. Refer to «Fastener Tightening Specifications»(/chevrolet/express-g2500/2013-2013/remont/horns/#horn-system__fastener-tightening-specifications) .
  3. Debris in the joint where the horns attach to the vehicle.
  4. Debris in direct contact with the horn
  5. Vehicle components vibrating while the horn is sounding

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/express-g2500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/chevrolet/express-g2500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/express-g2500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  4. «Wiring Repairs»(/chevrolet/express-g2500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__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 below.
  3. Connect a 15 A fused jumper wire between the horn fused 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 below. If the sound emitted is not clear and even, refer to Horn - Poor Tone below.

Horn Switch Circuit Test

  1. Ignition OFF, disconnect the X2 harness connector at the horn switch.
  2. Test for less than 1 ohms 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 the harness connector at the horn switch.
  4. Disconnect the X3 harness connector at the underhood fuse block.
  5. Connect a test lamp between B+ and the control circuit terminal 49.
  6. Press and release the horn pad. 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.
  7. Connect the X3 harness connector at the underhood fuse block. Disconnect the harness connector at the horn assembly.
  8. 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.
  9. 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 ohms 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 pad. 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 circuit fuse is good, test the control circuit for an open/high resistance. If the circuit tests normal, replace the underhood fuse block. If the test lamp is always OFF and the circuit 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 circuits 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 ohms between the 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 ohms between the control circuit terminal 53 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 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 20 A fused jumper wire between the control terminal B and 12 V. Install a jumper wire between the ground terminal A and ground. Verify the horns emit 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 repair.

  1. «Body Wiring Harness Junction Block Replacement»(/chevrolet/express-g2500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-repair-instructions)
  2. «Horn Replacement»(/chevrolet/express-g2500/2013-2013/remont/horns/#horn-system)
  3. «Steering Wheel Horn Switch Replacement»(/chevrolet/express-g2500/2013-2013/remont/horns/#horn-system)
  4. «Control Module References»(/chevrolet/express-g2500/2013-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for BCM replacement, programming and setup

Removal Procedure

  1. Raise and support the hood.
  2. Disconnect the electrical connectors from the horn assembly.
  3. Remove the nut (2) that retains the horn mounting bracket (1) to the vehicle.
  4. Remove the horn assembly from the vehicle.
  5. Note the location of the trumpet mouth relative to the mounting bracket.
  6. Remove the nut holding the horn to the mounting bracket.
  7. Remove the horn from the mounting bracket.

Installation Procedure

  1. Install the horn to the mounting bracket.
  2. Line up the trumpet mouth in the same direction as the original.
  3. Install the nut holding the horn to the mounting bracket and tighten to 10 N.m (90 lb in).
  4. Install the horn assembly to the vehicle.
  5. Install the nut (2) in order to retain the horn mounting bracket (1) to the vehicle and tighten to 25 N.m (18 lb ft).
  6. Connect the electrical connectors to the horn assembly.
  7. Close the hood.
  1. Disable the SIR system. Refer to «SIR Disabling and Enabling»(/chevrolet/express-g2500/2013-2013/remont/airbag/#supplemental-inflatable-restraint-system__sir-disabling-and-enabling) .
  2. Remove the inflator module. Refer to «Airbag Steering Wheel Module Replacement»(/chevrolet/express-g2500/2013-2013/remont/airbag/#supplemental-inflatable-restraint-system) .
  3. Remove the horn plunger from the steering column by pressing inward to the stop and rotating horn plunger 90 degrees.
  4. Remove the horn contact plate retaining screws from the steering wheel.
  5. Remove the horn plunger from the steering wheel.
  1. Install the horn plunger to the steering wheel.
  2. Install the horn contact plate retaining screws to the steering wheel and tighten to 5.5 N.m (49 lb in).
  3. Install the horn plunger to the steering column.
  4. Install the inflator module. Refer to «Airbag Steering Wheel Module Replacement»(/chevrolet/express-g2500/2013-2013/remont/airbag/#supplemental-inflatable-restraint-system) .
  5. Enable the SIR system. Refer to «SIR Disabling and Enabling»(/chevrolet/express-g2500/2013-2013/remont/airbag/#supplemental-inflatable-restraint-system__sir-disabling-and-enabling) .

System Description

The horn system consists of the following components

  1. The HORN fuse
  2. The Horn relay
  3. The Horn Contact
  4. The Horn Assembly
  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»(/chevrolet/express-g2500/2013-2013/remont/door-locks-anti-theft-systems/#keyless-entry-system-and-remote-functions__keyless-entry-system-description-and-operation) . 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»(/chevrolet/express-g2500/2013-2013/remont/door-locks-anti-theft-systems/#keyless-entry-system-and-remote-functions__keyless-entry-system-description-and-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 horns through the horn control circuit. The horns sound as long as ground is applied to the horn relay control circuit.