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. |
Diagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Horn Relay Control | 1 | 2 | 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 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
Connector End View Reference
Electrical Information Reference
Scan Tool Reference
Circuit/System Testing
With a test lamp connected to ground, probe each of the test points on the HORN fuse while activating the horns. The test lamp should illuminate at one or both of the fuse test points.
| ⇒ | If the test lamp does not illuminate at either test point, refer to the Horn Switch Test. |
| ⇒ | If the test lamp illuminates, refer to the Horn Test. |
Horn Switch Test
- Ignition OFF, disconnect the (C1) harness connector at the inflatable restraint steering wheel module coil.
- Ignition ON, test for B+ between the horn relay control circuit terminal J and ground.
- Momentarily connect a 3A fused jumper wire between the control circuit terminal J and ground. The horns should work.
- If all circuits test normal, test or replace the horn switch.
Important: The inflatable restraint steering wheel module coil harness connector and the horn switch are located under the inflatable restraint steering wheel module. To disable the SIR system refer to SIR Disabling and Enabling .
| ⇒ | If less than B+, test the control circuit for an open/high resistance. If the circuit tests normal, replace the underhood fuse block. |
| ⇒ | If the horns do not work, replace the underhood fuse block. |
Horn Test
- Ignition OFF, disconnect the harness connector at the horns.
- Test for less than 1 ohm of resistance between the ground circuit terminal A and ground.
- Connect a test lamp between the control circuit terminal B and ground.
- Ignition ON, press and release the horn switch. The test lamp should turn ON and OFF when pressing and releasing the horn switch.
- If all circuits test normal, test or replace the horns.
| ⇒ | If greater than 1 ohm, test the ground circuit for an open/high resistance. |
| ⇒ | If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
