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 |
|---|---|---|---|---|
Relay Coil B+ | 1 | 1 | -- | -- |
Relay Switch B+ | 1 | 1 | -- | -- |
Relay Control | 2 | 1 | -- | -- |
Horn Control | 1 | 1 | 2 | -- |
Horn Switch Ground | -- | 1 | -- | -- |
Horn Ground | -- | 1 | -- | -- |
1. Horn Inoperative 2. Horn Always On | ||||
Circuit/System Description
The horn is controlled by the horn relay through a high side drive control circuit. When the relay is energized battery voltage will be supplied to the horn through the horn control circuit. The horn relay is controlled by the horn switch through a low side drive control circuit. Battery voltage is supplied to the relay coil at all times and when the horn switch is pressed the relay control circuit is grounded and the relay will be energized.
Reference Information
Schematic Reference
Connector End View Reference
Description and Operation
Horns System Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Testing
- Ignition OFF, disconnect the horn relay.
- Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 87 and ground.
- Verify that a test lamp illuminates between the B+ circuit terminal 86 and ground.
- Verify that a test lamp illuminates between the B+ circuit terminal 30 and ground.
- Disconnect the harness connector at the horn.
- Test for less than 10 ohms between the horn ground circuit terminal 1 and ground
- Connect the harness connector at the horn.
- Connect a 15A fused jumper wire between the B+ circuit terminal 30 and the horn control circuit terminal 87. Verify the horn is activated.
- Disconnect the harness connector at the horn switch.
- Test for less than 10 ohms between the switch ground circuit terminal and ground
- Connect the harness connector at the horn switch.
- Connect a test lamp between the B+ circuit terminal 86 and the relay control circuit terminal 85.
- Press and release the horn switch. The test lamp should turn ON and OFF when changing between the commanded states.
- If all circuits test normal, test or replace the horn relay.
| ⇒ | If the test lamp illuminates, test the control circuit for a short to voltage. |
| ⇒ | 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 horn control circuit terminal 87 for a short to ground. If the circuit tests normal, test or replace the horn relay. |
| ⇒ | If the test lamp does not illuminate, test the B+ circuit for an open/high resistance. |
| ⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
| ⇒ | If the horn does not activate, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the horn. |
| ⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
| ⇒ | If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the 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, replace the horn switch. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
