Interior Backlighting Malfunction
Interior Backlighting Malfunction
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.
Diagnostic Fault Information
Circuit/System Description
The body control module (BCM) supplies a voltage reference 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 through the backlight lamp control circuit, and the LED dimming control circuit illuminating the LEDs and backlight lamps.
Reference Information
Schematic Reference
Interior Lights Dimming Schematics Interior Lights Dimming Schematics
Connector End View Reference
Component Connector End Views Sunshade - Left (DH6)
Description and Operation
Interior Lighting Systems Description and Operation Interior Lighting Systems
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
Scan Tool Reference
Control Module References Control Module References for scan tool information
Circuit/System Verification
1. Ignition ON, observe the scan tool Indicator Backlight Command parameter while operating the dimmer switch from high to low. The parameter should indicate between 5-50 percent when the backlight switch is moved up and down.
• If the reading does not change, refer to Dimmer Switch Circuit Test.
2. Command the LED Backlight Dimming test with the scan tool. The appropriate incandescent lighting items should go ON and OFF.
• If the backlighting does not go ON and OFF, refer to Interior Backlighting Circuit Test.
Circuit/System Testing
Dimmer Switch Circuit Test
1. Ignition OFF, disconnect the harness connector at the S30 Headlamp Switch.
2. Ignition ON, test for greater than 11 V between the 12 V reference circuit terminal 1 and ground.
• If greater than the specified range, test the 12 V reference circuit for a short to voltage. If the circuit tests normal, replace the K9 Body Control Module.
• If less than the specified range, test the 12 V reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K9 Body Control Module.
3. Ignition ON, test for less than 0.3 V between dimming signal circuit terminal 12 and ground.
• If greater than the specified range, test the dimming signal circuit terminal 12 for a short to voltage. If the circuit tests normal, replace the K9 Body Control Module.
4. Install a 3 A fused jumper wire between the signal circuit terminal 12 and the 12 V reference circuit terminal 1. The interior backlighting should now be dimmed.
• If the interior backlighting is not dimmed, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K9 Body Control Module.
5. If all circuits test normal, test or replace the S30 Headlamp Switch.
Interior Backlighting Circuit Test
1. Ignition OFF, disconnect the harness connectors at the appropriate inoperative backlighting component.
2. Test for less than 5 ohms between wiring color BK of the appropriate component and ground.
• If greater than the specified range, test the ground circuit for an open/high resistance.
3. Connect a test lamp between wiring color YE of the appropriate component and ground.
4. Command with the scan tool the LED Backlight Dimming test the illumination ON/OFF.
• If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K9 Body Control Module.
• 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.
5. If all circuit test normal, test or replace the appropriate inoperative backlighting component.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Dome and Reading Lamp Replacement Dome and Reading Lamp Replacement
* Sunroof Switch Replacement Sunroof Switch Replacement
* Outside Remote Control Rearview Mirror Switch Replacement Service and Repair
* Front Side Door Window Switch Replacement (Passengers Side Door) Front Side Door Window Switch Replacement (Passengers Side Door)
* Rear Side Door Window Switch Replacement Rear Side Door Window Switch Replacement
* Rear Compartment Courtesy Lamp Replacement Rear Compartment Courtesy Lamp Replacement
* Steering Wheel Airbag Replacement Steering Wheel Airbag Replacement
* Headlamp Switch Replacement Service and Repair
* Instrument Panel Multifunction Switch Replacement Service and Repair
* Ignition Lock Cylinder Replacement (Without BTM) Ignition Lock Cylinder Replacement (Without BTM)
* Instrument Panel Multifunction Switch Replacement Service and Repair
* Body Control Module Replacement Body Control Module Replacement
* Control Module References Control Module References for BCM, HVAC, instrument panel cluster, or radio replacement, programming and setup