2010 Cadillac Truck SRX AWD V6-3.0L Page 729
DTC B3891 04
- Trailer Fog Lamps Circuit Open
Diagnostic Fault Information
Circuit/System Description
The trailer brake control module will receive a serial data message from the BCM indicating that the vehicle rear fog lamps have been activated.
The trailer brake control module will then apply system voltage to the trailer fog lamps through their respective voltage supply circuits.
Conditions for Running the DTC
When the trailer fog lamps are turned on.
Conditions for Setting the DTC
B3891 02
The trailer brake control module detects a short to ground on the trailer fog lamp control circuit.
B3891 04
The trailer brake control module detects an open/high resistance on the trailer fog lamp control circuit.
Action Taken When the DTC Sets
The trailer fog lamps will be 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 40 ignition cycles.
Reference Information
Schematic Reference
Trailer Connector/Provision Schematics (See: Diagrams/Electrical Diagrams/Starting and Charging/Power and Ground Distribution/System
Diagram/Trailer Connector/Provision Schematics)
Connector End View Reference
Component Connector End Views (See: Diagrams/Connector Views/Connector End Views By Name)
Description and Operation
Exterior Lighting Systems Description and Operation (See: Lighting and Horns/Description and Operation/Exterior Lighting Systems)
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
Ignition ON, observe the function of the trailer fog lamps while commanding the Trailer Fog Lamp ON and OFF with a scan tool. The trailer fog
lamps should turn ON and OFF while changing between the commanded states.
