* 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 (See: Lighting and Horns/Horn/Diagrams/Electrical Diagrams)
Connector End View Reference
Component Connector End Views (See: Diagrams/Connector Views)
Description and Operation
Horns System Description and Operation (See: Lighting and Horns/Horn/Description and Operation)
Electrical Information Reference
* Circuit Testing (See: Testing and Inspection/Component Tests and General Diagnostics/General Electrical Diagnostic Procedures/Circuit
Testing/Circuit Testing)
* Connector Repairs (See: Testing and Inspection/Component Tests and General Diagnostics/General Electrical Diagnostic
Procedures/Connector Repairs/Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (See: Testing and Inspection/Component Tests and General Diagnostics/General
Electrical Diagnostic Procedures/Circuit Testing/Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (See: Testing and Inspection/Component Tests and General Diagnostics/General Electrical Diagnostic Procedures/Wiring
Repairs/Wiring Repairs)
Scan Tool Reference
Control Module References (See: Testing and Inspection/Programming and Relearning) for scan tool information
Circuit/System Verification
Command the horn ON and OFF with the scan tool. The horn should turn ON and OFF when changing between the commanded states.
Circuit/System Testing
1. Ignition OFF, disconnect the X4 harness connector at the underhood fuse block.
2. Connect a test lamp between the control circuit terminal G1 and B+.
3. Press and release the horn switch. The test lamp should turn ON and OFF when changing between the commanded states.
锟斤拷 If the test lamp is always ON, test the control circuit for a short to ground or a sticking horn switch. If the circuit tests normal, replace the
BCM.
锟斤拷 If the test lamp is always OFF, test the control circuit for a short to voltage, an open high resistance, or a horn switch which is not closing.
If the circuit tests normal, replace the BCM.
4. If all circuits test normal, replace the underhood fuse block.
Repair Instructions
Perform the Diagnostic Repair Verification (See: Verification Tests) after completing the diagnostic procedure.
* Underhood Electrical Center or Junction Block Bracket Replacement (See: Maintenance/Fuses and Circuit Breakers/Fuse Block/Service and
Repair/Removal and Replacement/Underhood Electrical Center or Junction Block Bracket Replacement)
* Control Module References (See: Testing and Inspection/Programming and Relearning) for BCM replacement, setup and programming
B2850
DTC B2850, B2855, B2870, or B2875
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic System
Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Strategy Based Diagnosis) for an
overview of the diagnostic approach
* Diagnostic Procedure Instructions (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic Procedure
Instructions) provides an overview of each diagnostic category
