B2750
DTC B2750
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 Descriptors
DTC B2750
- Horn Relay Secondary Circuit
For symptom byte information refer to: Symptom Byte List Symptom Byte List
Diagnostic Fault Information
Circuit/System Description
The Body Control Module (BCM) provides a ground for the Horn printed circuit board relay within the underhood fuse block. The underhood fuse block will then provide B+ voltage to the horn control circuit, sounding 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 relay coil control circuit.
B2750 02
The BCM detects a short to ground in the relay coil control circuit.
B2750 04
The BCM detects an open/high resistance in the relay coil control circuit.
Action Taken When the DTC Sets
* If B2750 01 or B2750 04 is current, the horns will be inoperative.
* If B2750 02 is current, the horns will sound continuously until the horn is disconnected or when the horns overheat and becomes inoperative.
Conditions for Clearing the DTC
* The DTC will be current for as long as the fault is present.
* When the fault is no longer present, the DTC will be a history DTC.
* A history DTC will clear after 50 ignition cycles.
Reference Information
Schematic Reference
Horn Schematics Electrical Diagrams
Connector End View Reference
Component Connector End Views Fuel Pump and Level Sensor Assembly
Description and Operation
Horns System Description and Operation Description and Operation
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
Scan Tool Reference
Control Module References Control Module References for scan tool information
Circuit/System Verification
1. Ignition ON.
2. Verify the P12A Horn-High Note and the P12B Horn-Low Note turns On and Off when commanding the Horn Relay On and Off with a scan tool.
• If the P12A Horn-High Note and the P12B Horn-Low do not turn On and Off
Refer to Circuit/System Testing.
• If the P12A Horn-High Note and the P12B Horn-Low turn On and Off
3. All OK.
Circuit/System Testing
1. Ignition OFF, disconnect the X2 harness connector at the X50A Fuse Block-Underhood.
2. Connect a test lamp between the control circuit terminal 25 and B+, ignition ON.
3. Verify the test lamp turns ON and OFF when commanding the Horn Relay On and Off with a scan tool.
• If the test lamp is always OFF
1. Ignition OFF, disconnect the harness connector at the K9 Body Control Module, ignition ON.
2. Test for less than 1 V between the control circuit and ground.
• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V
3. Ignition OFF.
4. Test for less than 2 ohms in the control circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the K9 Body Control Module.
• If the test lamp is always ON
1. Ignition OFF, disconnect the harness connector at the K9 Body Control Module.
2. Test for infinite resistance between the control circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance, replace the K9 Body Control Module.
• If the test lamp turns ON and OFF
4. Replace the X50A Fuse Block-Underhood.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the repair.
* Front Compartment Fuse Block Replacement Front Compartment Fuse Block Replacement
* Control Module References Control Module References for BCM replacement, programming and setup