When the rear fog lamp switch is placed in the ON position, ground is applied to the auxiliary body control module (XBCM) through the rear fog
lamp switch circuit. The XBCM then applies voltage to the rear fog lamp control circuit to the rear fog lamp.
Conditions for Running the DTC
* Battery voltage must be between 9-16 V.
* Rear fog lamps ON.
Conditions for Setting the DTC
B2540 02
The BCM detects a short to ground in the rear fog lamp switch signal circuit.
B2540 05
The BCM detects a short to voltage or an open/high resistance in the rear fog lamp switch signal circuit.
Action Taken When the DTC Sets
The rear fog lamps will not operate when the park lamps are ON and the rear fog lamp switch is active.
Conditions for Clearing the DTC
* The condition responsible for setting the DTC no longer exists.
* A history DTC will clear once 100 consecutive malfunction-free ignition cycles have occurred.
Reference Information
Schematic Reference
Fog Lights Schematics (See: Diagrams/Electrical Diagrams/Lighting and Horns/System Diagram/Fog Lights Schematics)
Connector End View Reference
Component Connector End Views (See: Diagrams/Connector Views)
Description and Operation
Exterior Lighting Systems Description and Operation (See: Lighting and Horns/Description and Operation/Exterior Lighting Systems 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 Testing
1. Ignition OFF, disconnect the harness connector at the headlamp switch.
2. Verify that a test lamp illuminates between B+ and the ground circuit terminal 8.
锟斤拷 If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
3. Ignition ON, verify the scan tool Rear Fog Lamp Switch parameter is INACTIVE.
锟斤拷 If not the specified value, test the signal circuit terminal 6 for a short to ground. If the circuit tests normal, replace the XBCM.
4. Install a 3 A fused jumper wire between the signal circuit terminal 6 and ground. Verify the scan tool Rear Fog Lamp Switch parameter is
ACTIVE.
锟斤拷 If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the
