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 Descriptors
DTC B2750 01: Horn Relay Secondary Circuit Short to BatteryDTC B2750 02: Horn Relay Secondary Circuit Short to Ground
DTC B2750 04: Horn Relay Secondary Circuit Open
Diagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Horn Relay B+ | 2 | 2 | -- | -- |
Horn Switch Signal | 1 | 2 | 2 | -- |
Horn Relay Control | B2750 02 | B2750 04 | B2750 01 | -- |
Horn Control | 2 | 2 | 1 | -- |
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 horn.
Conditions for Running the DTC
When the horn output is actively being requested by the BCM.
Conditions for Setting the DTC
B2750 01
The BCM detects a short to voltage in the horn relay control circuit.
B2750 02
The BCM detects a short to ground in the horn relay control circuit.
B2750 04
The BCM detects an open/high resistance in the horn relay control circuit.
Action Taken When the DTC Sets
B2750 01, B2750 04
The horn will be inoperative.
B2750 02
The horn will sound continuously until the horn is disconnected or when the horn overheats and becomes inoperative.
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
Control Module References for scan tool information
Circuit/System Verification
Ignition ON, command the Horn Relay ON and OFF with the scan tool. The horn 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 85 and ground.
- Connect a test lamp between the control circuit terminal 86 and the B+ circuit terminal 85.
- Command the Horn Relay 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 a short to ground or an open/high resistance. |
| ⇒ | 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 K9 BCM. |
| ⇒ | If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the K9 BCM. |
Component Testing
- Ignition OFF, disconnect the HORN relay.
- Test for 60-180 ohms between terminals 85 and 86.
- Test for infinite resistance between the following terminals:
- Install a 30A 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 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 |
