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 | 2 | --
Horn Switch Ground | -- | 2 | 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 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

1. Ignition ON, press and release the steering wheel horn pad. The horns should sound and emit a clear and even tone only when the horn pad is pressed.

⇒ | If the horns do not sound when the horn pad is pressed or continues sounding after the horn pad is released, refer to Horn Switch Circuit Test.

⇒ | If the sound emitted from the horns are not clear and even, refer to Horn - Poor Tone.

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

⇒ | If the horns do not turn ON and OFF when changing between the commanded states, refer to Horn Circuit Test.

### Circuit/System Testing

#### Horn Switch Circuit Test

1. Ignition OFF, disconnect the X1 harness connector at the inflatable restraint steering module coil.
2. Test for less than 1 ohm between the ground circuit terminal G and ground.

⇒ | If greater than the specified range, test the ground circuit for an open/high resistance.

3. Reconnect the harness connector at the horn switch and disconnect the HORN relay.
4. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 87 and ground.

⇒ | If the test lamp illuminates, test the control circuit for a short to voltage.

5. Verify that a test lamp illuminates between the B+ circuit terminal 85 and ground.

⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test the control circuit for a short to ground. If the circuit tests normal, test or replace the HORN relay.

6. Verify that a test lamp illuminates between the B+ circuit terminal 30 and ground.

⇒ | If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.

7. Ignition OFF, disconnect the harness connector at the appropriate horn.
8. Test for less than 1 ohm between the ground circuit connector X2, terminal A and ground.

⇒ | If greater than the specified range, test the ground circuit for an open/high resistance.

9. Connect the harness connector at the appropriate horn.
10. Ignition ON, connect a 15A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87. Verify the horns are activated.

⇒ | If the horns do not activate, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the appropriate horn.

11. Connect a test lamp between the B+ circuit terminal 85 and the control circuit terminal 86.
12. Press and release the steering wheel 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. If the circuit tests normal, inspect for a sticking horn switch.

⇒ | 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, inspect for an open horn switch.

⇒ | If all circuits test normal, test or replace the HORN relay.

#### Horn - Poor Tone

1. Ignition OFF, disconnect the harness connector at the appropriate horn.
2. Test for less than 1 ohm between the horn ground circuit connector X2, terminal A and ground.

⇒ | If greater than the specified range, test the ground circuit for a high resistance.

3. Disconnect the HORN relay.
4. Test for less than 1 ohm between the control circuit terminal 87 and the control circuit connector X1, terminal A at the horn.

⇒ | If greater than the specified range, test the control circuit for an open/high resistance.

5. If all circuits test normal, test or replace the horn.

#### Horn Circuit Test

1. Ignition OFF, disconnect the HORN relay.
2. Connect a test lamp between the B+ circuit terminal 85 and the control circuit terminal 86.
3. Ignition ON, 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 ON, test the control circuit for a short to ground. If the circuit tests normal, replace the BCM.

⇒ | If the test lamp is always OFF, test circuit the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.

### Component Testing

#### Horn Test

1. Ignition OFF, disconnect the harness connector at the appropriate horn.
2. Install a 15A fused jumper wire between the control connector X1, terminal A and 12 volts. Install a jumper wire between the ground connector X2, 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.

#### Relay Test

1. Ignition OFF, disconnect the HORN relay.
2. Test for 60-180 ohms between terminals 85 and 86.

⇒ | If not within the specified range, replace the relay.

3. Test for infinite resistance between the following terminals:

• | 30 and 86

• | 30 and 87

• | 30 and 85

• | 85 and 87

⇒ | If not the specified value, replace the relay.

4. Install a 30-amp fused jumper wire between relay terminal 85 and 12 volts. Install a jumper wire between relay terminal 86 and ground. Test for less than 2 ohms between terminals 30 and 87.

⇒ | If greater than the specified range, replace the relay.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Horn Replacement .

• | Inflatable Restraint Steering Wheel Module Replacement .

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