B2752
DTC B2752
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions)provides an overview of each diagnostic category.
DTC Descriptor
DTC B2752
- Horn Relay Coil Circuit Low
Diagnostic Fault Information
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
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 in the horn relay control circuit or a horn switch stuck or pressed for greater than 60 seconds.
Action Taken When the DTC Sets
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
Horn Schematics (Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector End Views By Name)
Description and Operation
Horns System Description and Operation (Description and Operation)
Electrical Information Reference
* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)
Scan Tool Reference
Control Module References (Programming and Relearning)for scan tool information
Circuit/System Verification
Ignition ON, command the Horn ON and OFF with the scan tool. The horns should turn ON and OFF when changing between the commanded states.
Circuit/System Testing
1. Ignition OFF, disconnect the X2 harness connector at the BCM.
2. Connect a test lamp between the control circuit terminal A25 and B+.
3. Press and release the horn pad, the test lamp should illuminate each time the horn pad is pressed.
• If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, inspect for a stuck horn switch.
4. Connect the X2 harness connector at the BCM and disconnect the HORN relay.
5. Connect a test lamp between the relay coil B+ circuit and the relay coil control circuit.
6. Ignition ON, command the Horn ON and OFF with the 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.
7. If all circuits test normal, replace the HORN relay.
Component Testing
Relay Test
1. Ignition OFF, disconnect the HORN relay.
2. Test for 60-180 ohm 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 30A fused jumper wire between relay terminal 85 and 12V. Install a jumper wire between relay terminal 86 and ground. Test for less than 2 ohm between terminals 30 and 87.
• If greater than the specified range, replace the relay.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Relay Replacement (Attached to Wire Harness) (Relay Replacement (Attached to Wire Harness))Relay Replacement (Within an Electrical Center) (Relay Replacement (Within an Electrical Center))
* Control Module References (Programming and Relearning)for BCM replacement, setup and programming