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 Testing
1. Inspect the trailer rear fog lamp bulb for an open or shorted filament.
锟斤拷 If the bulb is inoperable, replace the bulb.
2. Park lamp switch OFF, clear the DTC, test the trailer rear fog lamp circuit for a short to voltage, short to ground, an open, or high resistance.
锟斤拷 If all circuits/connections test normal, replace the XBCM.
Repair Instructions
Perform the Diagnostic Repair Verification (See: Verification Tests) after completing the diagnostic procedure.
Control Module References (See: Testing and Inspection/Programming and Relearning) for XBCM replacement, setup, and programming
Gasoline With LY6, or Diesel
DTC B3894 (Gasoline With LY6, or Diesel)
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) provide an overview of each diagnostic category.
DTC Descriptor
DTC B3894 5A
- Stop Lamp Switch Circuit Plausibility Failure
Circuit/System Description
The brake switch is hard wired to the trailer brake control module (TBCM). The body control module (BCM) sends a brake switch status serial data
message to the trailer brake control module. The trailer brake control module compares the states of the brake switch signal to the serial data
message after a master cylinder brake pressure sensor threshold is exceeded. If the brake switch signal and the serial data message are not in
agreement or if the serial data message is not valid, a DTC will set and the trailer brake control system will be disabled.
Conditions for Running the DTC
* Battery voltage is 9.5-17 V.
* The module initialization has taken place.
* The master cylinder brake pressure exceeds threshold
Conditions for Setting the DTC
* The brake switch serial data message is not valid.
* The actual brake switch input to the trailer brake control module, and the serial data information for the brake switch do not match.
Action Taken When the DTC Sets
* The trailer brake control will be disabled for the remainder of the ignition cycle.
* The driver information center will display Service Trailer Brake System.
Conditions for Clearing the DTC
* The condition for the DTC is no longer present.
