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DTC B260A

DTC B260A

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 Descriptor

DTC B260A 00

Backlight and Display Dimming Request Circuit Malfunction

Diagnostic Fault Information

Circuit Short to Ground Open/High Resistance Short to Voltage Signal Performance
Backlight and Display Dimming Request Signal

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B260A



Circuit/System Description

The body control module (BCM) supplies a reference voltage to the backlight dimmer switch, which is part of the headlamp switch. When the backlight dimmer switch is placed in a desired brightness position, reference voltage is applied through the backlight dimmer switch rheostat to the BCM. The BCM interprets this voltage signal, then applies a pulse width modulated (PWM) voltage to the LED dimming supply circuit to all related interior lamps, illuminating them to the desired level of brightness.

Conditions for Running the DTC

The ignition is ON. Parklamps are illuminated.

Conditions for Setting the DTC

The BCM detects the instrument panel dimmer switch is ON for greater than 60 seconds.

Action Taken When the DTC Sets

The BCM will not dim or illuminate any LED backlighting supplied by the backlight lamp control circuits.

Conditions for Clearing the DTC


• The condition responsible for setting the DTC no longer exists.

• A history DTC will clear once 100 consecutive malfunction ignition cycles have occurred.


Reference Information

Schematic Reference

Interior Lights Dimming Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Interior 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, switch ON exterior lighting, vary the interior backlight from dim to full bright by using the dimmer switch. The interior backlighting should dim and then become full bright.

Circuit/System Testing


1. Ignition OFF, disconnect the harness connector at the S30 Headlamp Switch.

2. Ignition OFF, test for less than 5 Ω between the low reference circuit terminal 6 and ground.

3. If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the K9 Body Control Module.

4. Connect a test lamp between the S30 Headlamp Switch harness connector terminal 1 and ground.

5. Command with the scan tool the LED Backlight Dimming test the illumination ON/OFF.

6. If the test lamp cannot be dimmed test the control circuit for a short to voltage or replace the K9 Body Control Module.

7. If greater than the specified range, test the 5 V reference circuit for a short to voltage. If the circuit tests normal, replace the K9 Body Control Module.

8. Verify the scan tool LED Backlight Dimming Command is less than 40-55%.

9. If not the specified range, test the signal circuit terminal 12 for a short to voltage. If the circuit tests normal, replace the K9 Body Control Module.

10. Install a 3 A fused jumper wire between the signal circuit terminal 12 and the high reference circuit terminal 1. Verify the scan tool LED Backlight Dimming Command is at 5%..

11. If more than the specified value, you must test the signal circuit for a short to ground or an open circuit/high resistance. If the circuit tests normal, replace the K9 Body Control Module.

12. If all circuits test normal, test or replace the S30 Headlamp Switch.


Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.


• Headlamp Switch Replacement

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