2010 Cadillac Truck Escalade RWD V8-6.0L Hybrid Page 621
瀚慖f the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the BCM.
瀚慖f the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace
the BCM.
11. If all circuits test normal, test or replace the fog lamp relay.
Repair Instructions
Perform the Diagnostic Repair Verification (See: Verification Tests) after completing the diagnostic procedure.
* Relay Replacement (Attached to Wire Harness) (See: Power and Ground Distribution/Power Distribution Relay/Service and Repair/Relay
Replacement (Attached to Wire Harness))Relay Replacement (Within an Electrical Center) (See: Power and Ground Distribution/Power
Distribution Relay/Service and Repair/Relay Replacement (Within an Electrical Center))
* Front Fog Lamp Replacement (Tahoe, Avalanche) (See: Lighting and Horns/Fog/Driving Lamp/Service and Repair/Removal and
Replacement/Front Fog Lamp Replacement (Tahoe, Avalanche))Front Fog Lamp Replacement (Yukon) (See: Lighting and
Horns/Fog/Driving Lamp/Service and Repair/Removal and Replacement/Front Fog Lamp Replacement (Yukon))Front Fog Lamp
Replacement (PLATINUM) (See: Lighting and Horns/Fog/Driving Lamp/Service and Repair/Removal and Replacement/Front Fog Lamp
Replacement (Platinum))
* Control Module References (See: Testing and Inspection/Programming and Relearning) for BCM replacement, setup, and programming
B2540
DTC B2540
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.
DTC Descriptors
DTC B2540 02
- Rear Fog Lamp Control Circuit Short to Ground
DTC B2540 05
- Rear Fog Lamp Control Circuit Short to Battery or Open
Diagnostic Fault Information
Circuit/System Description
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.
