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DTC B2750

DTC B2750

Diagnostic Instructions


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

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

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


DTC Descriptors

DTC B2750 01

Horn Relay Secondary Circuit Short to Battery

DTC B2750 02

Horn Relay Secondary Circuit Short to Ground

DTC B2750 04

Horn Relay Secondary Circuit Open

Diagnostic Fault Information

Circuit Short to Ground Open/High Resistance Short to Voltage Signal Performance
Horn Switch Signal 1 2 2 -
Horn Relay Control B2750 02 B2750 04 B2750 01 -
Horn Control 2 2 1 -
Horn Ground - 2 2 -
1. Horn Always On 2. Horn Inoperative


Circuit/System Description

The BCM provides a ground for the Horn PCB relay within the underhood fuse block. The underhood fuse block will then provide B+ voltage to the horn control circuit, sounding the horn.

Conditions for Running the DTC

When the horn output is actively being requested by the BCM.

Conditions for Setting the DTC

B2750 01

The BCM detects a short to voltage in the horn relay control circuit.

B2750 02

The BCM detects a short to ground in the horn relay control circuit.

B2750 04

The BCM detects an open/high resistance in the horn relay control circuit.

Action Taken When the DTC Sets

B2750 01, B2750 04

The horn will be inoperative.

B2750 02

The horn will sound continuously until the horn is disconnected or when the horn overheats and becomes inoperative.

Conditions for Clearing the DTC


• The DTC clears when the fault is no longer detected.

• The current DTC will become history when the request for the output is removed.

• The history DTC will clear after 50 consecutive fault-free ignition cycles have occurred.


Reference Information

Schematic Reference

Horn Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Horns System Description and Operation

Electrical Information Reference


• Circuit Testing

• Connector Repairs

• Testing for Intermittent Conditions and Poor Connections

• Wiring Repairs


Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

Ignition ON, command the Horn Relay Command ON and OFF with the scan tool. The horn should turn ON and OFF when changing between the commanded states.

Circuit/System Testing


1. Ignition OFF, disconnect the X2 harness connector at the X50A underhood fuse block.

2. Connect a test lamp between the control circuit terminal 25 and B+.

3. Ignition ON, command the Horn Relay Command ON and OFF with the scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

4. 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 K9 BCM.

5. If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the K9 BCM.

6. If all circuits test normal, replace the X50A underhood fuse block.


Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for BCM replacement, programming and setup.