For 1990-2009 cars

### Diagnostic Instructions

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

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

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

### DTC Descriptor

DTC B2750 01: Horn Relay Control Circuit Short to Battery

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Horn Relay Control Circuit | B2750 01 | -- | B2750 01 | --

### Circuit/System Description

Battery positive voltage is applied at all times to the horn relay coil and horn relay switch. Pressing the horn switch applies ground to the horn relay control circuit. The body control module (BCM) also may apply 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 via the horn control circuit. The horn will sound as long as ground is applied to the horn relay control circuit.

### Conditions for Running the DTC

The BCM monitors the voltage level on the horn relay control circuit whenever the ignition is in the RUN position.

### Conditions for Setting the DTC

The BCM will set DTC B2750 as current whenever an improper voltage level is detected on the horn relay control circuit for more than 15 seconds.

### Action Taken When the DTC Sets

The BCM will disable the driver for the horn relay control circuit whenever DTC B2750 is set as current.

### Conditions for Clearing the DTC

DTC B2750 will clear when an improper voltage level is no longer detected on the horn relay control circuit, or when a scan tool is used to clear DTCs.

### Diagnostic Aids

Inspect for a sticking horn pad or horn switch.

### Reference Information

#### Schematic Reference

Horn Schematics

#### Connector End View Reference

Horn 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

• | Scan Tool Data List

• | Scan Tool Data Definitions

• | Scan Tool Output Controls

### Circuit/System Verification

1. Press the horn switch. The horn relay should click and the horn should sound as long as the horn switch is pressed.
2. Turn ON the ignition. With a scan tool, command the BCM Horn Output. The horn relay should click and the horn should sound while commanded ON and stop sounding when commanded OFF.

### Circuit/System Testing

1. Ignition OFF, disconnect the horn relay.
2. Connect a test lamp between the relay coil B+ circuit and the relay coil control circuit.
3. Verify the test lamp turns ON and OFF when using the scan tool to command the horn relay.

⇒ | If the test fails to illuminate, test the horn relay control circuit for a short to voltage or an open. The horn relay control circuit includes the steering wheel coil assembly and horn switch. If the circuit/connections test normal, replace the BCM.

⇒ | If the test lamp remains illuminated at all times, test the horn relay control circuit for a short to ground. The horn relay control circuit includes the steering wheel coil assembly and horn switch. If the circuit/connections test normal, replace the BCM.

4. If all circuits test normal, test or replace the horn relay.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Inflatable Restraint Steering Wheel Module Coil Replacement

• | Relay Replacement

• | Control Module References for BCM replacement, setup, and programming