For 1990-2009 cars

### Diagnostic Fault Information

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

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Horn Relay Control | B2750 00 | B2750 00 | B2750 00 | --
Horn Control | 2 | 2 | 1 | --
Horn Ground | -- | 2 | -- | --
Horn Switch Ground | -- | 2 | -- | --
1. Horns Always ON 2. Horns Inoperative

### Circuit/System Description

When the horn button is pressed, ground is applied through the horn switch contacts and the horn relay control circuit to the coil side of the relay. The horn relay coil is then energized, causing the relay switch contacts to close applying voltage through the horn fuse and the horn control circuit to the horns. For theft deterrent functions, the body control module (BCM) also controls the horn relay by applying ground to the relay control circuit to the relay.

### Reference Information

#### Schematic Reference

Horn Schematics .

#### Connector End View Reference

Component Connector End Views .

#### Electrical Information Reference

• | Circuit Testing .

• | Connector Repairs .

• | Testing for Intermittent Conditions and Poor Connections .

• | Wiring Repairs .

#### Scan Tool Reference

Control Module References

### Circuit/System Verification

Ignition ON, use scan tool Horn output control to command the horn relay On. The Horn Relay Command output data parameter should display On and the horn should sound.

### Circuit/System Testing

1. Remove the HORN fuse from the underhood fuse block. The horns should turn OFF

⇒ | If the horns remain on, repair the short out voltage in the horn control circuit.

2. Ignition OFF, disconnect the BCM connector C5.
3. Test for a ground signal at the horn relay control terminal of the BCM connector.

⇒ | If a ground signal is not present, replace the underhood fuse block.

Important: The horn switch is located under the inflatable restraint steering wheel module. Disable the SIR system. Refer to SIR Disabling and Enabling .

4. Ignition OFF, disconnect the horn switch and test the switch for shorted contacts.

⇒ | If the switch does not function properly, replace.

5. Test for a short to ground in the horn relay control circuit.

⇒ | If the circuits/connectors test normal, replace the BCM.

### Repair Instructions

Perform the Diagnostic Repair Verification , after completing the diagnostic procedure.

• | Inflatable Restraint Steering Wheel Module Replacement .

• | Underhood Electrical Center or Junction Block Replacement .

• | Control Module References .