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DTC B2540

DTC B2540

Diagnostic Instructions


• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• Diagnostic Procedure Instructions has overviews of all diagnostic categories.


DTC Descriptors

DTC B2540 02

Rear Fog Lamps Control Circuit Short to Ground

DTC B2540 04

Rear Fog Lamps Control Circuit Open

Diagnostic Fault Information

Circuit Short to Ground Open/High Resistance Short to Voltage Signal Performance
Rear Fog Lamps Control

B2540 02

B2540 04

1

-

1. Rear fog lamp always ON



Circuit/System Description

The body control module (BCM) energizes the rear fog lamp by applying voltage to the rear fog lamp control circuit. When the rear fog lamp control circuit is energized the rear fog lamp is illuminated.

Conditions for Running the DTC

Rear fog lamp activated.

Conditions for Setting the DTC

B2540 02

The BCM detects a short to ground on the control circuit.

B2540 04

The BCM detects an open control circuit.

Action Taken When the DTC Sets

The appropriate fog lamp is inoperative.

Conditions for Clearing the DTC

The condition for setting the DTC is no longer present.

Reference Information

Schematic Reference

Fog Lights Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference


• Circuit Testing

• Connector Repairs

• Testing for Intermittent Conditions and Poor Connections

• Wiring Repairs


Scan Tool Reference

Control Module References for information on diagnostic tools

Circuit/System Verification

Ignition ON, perform the Rear Fog Lamp(s) Relay test. The rear fog lamp should be ON/OFF when changing between the commanded states.

Circuit/System Testing


1. Ignition OFF, disconnect the harness connector at the E29R Fog Lamp - Rear.

2. Test for less than 5 Ω between the E29R Fog Lamp - Rear harness connector terminal A and ground:

3. If greater than the specified value, test the appropriate ground circuit for an open circuit/high resistance.

4. Connect a test lamp between the E29R Fog Lamp - Rear harness connector terminal B and ground.

5. Ignition ON, perform the Rear Fog Lamps Relay Command test. The rear fog lamp should be ON/OFF when changing between the commanded states.

6. If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the K9 Body Control Module.

7. If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuits test normal, replace the K9 Body Control Module.

8. If all circuits test normal, test or replace the E29R Fog Lamp - Rear.


Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.


• Rear Fog Lamp Replacement

• Control Module References for information on BCM replacement, setup, and programming