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. |
DTC Descriptor
DTC B2750: Horn Relay Coil CircuitDiagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Horn Relay Control | B2750 | B2750 | B2750 | -- |
Horn Control | 2 | 2 | 1 | -- |
Horn Switch Ground | -- | 2 | 2 | -- |
Horn Ground | -- | 2 | 2 | -- |
1. Horn Always On 2. Horn Inoperative | ||||
Circuit/System Description
The body control module (BCM) controls the horn relay by grounding the control circuit of the horn relay coil energizing the relay. When the horn relay is energized, the horn relay contacts close applying voltage through the horn fuse and the horn control circuit to the horns.
Conditions for Running the DTC
The DTC can only set only when the output is actively being requested by the BCM.
Conditions for Setting the DTC
The BCM detects a short to ground, open, or short to voltage in the horn relay control circuit for approximately 125 milliseconds.
Action Taken When the DTC Sets
The BCM disables the output to the horn relay until the next ignition cycle.
Conditions for Clearing the DTC
| • | The DTC clears when the fault is no longer detected. |
| • | The current DTC will become history when the request for the output is removed. |
| • | The history DTC will clear after 50 consecutive fault-free ignition cycles have occurred. |
Reference Information
Schematic Reference
Connector End View Reference
Description and Operation
Horns System Description and Operation
Electrical Information Reference
Scan Tool Reference
Circuit/System Verification
Command the horns ON and OFF with the scan tool. The horns should turn ON and OFF when changing between the commanded states.
Circuit/System Testing
- Ignition OFF, disconnect the HORN relay.
- Ignition ON, verify a test lamp illuminates between the B+ circuit terminal K8 and ground.
- Connect a test lamp between the control circuit terminal M7 and B+.
- Command the horn ON and OFF with a scan tool. 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 does not illuminate, test the B+ circuit for an open/high resistance. If the circuit fuse is open, test the control circuit terminal M8 for a short to ground. If all circuits test normal, test or replace the HORN relay. |
| ⇒ | 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 BCM. |
| ⇒ | If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the BCM. |
Component Testing
- Ignition OFF, disconnect the HORN relay.
- Test for 60-180 ohms of resistance between terminals 85 and 86.
- Test for infinite resistance between the following terminals:
- 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 of resistance between terminals 30 and 87.
| ⇒ | If the resistance is not within the specified range, replace the relay. |
| • | 30 and 86 |
| • | 30 and 87 |
| • | 30 and 85 |
| • | 85 and 87 |
| ⇒ | If not the specified value, replace the relay. |
| ⇒ | If greater than the specified range, replace the relay. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for BCM replacement, setup, and programming. |
