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. 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 them to the desired level of brightness.
Reference Information
Schematic Reference
Interior Lights Dimming Schematics (Interior Lights Dimming Schematics)
Connector End View Reference
Component Connector End Views (Connector End Views By Name)
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 (Programming and Relearning) for scan tool information
Circuit/System Verification
1. Ignition ON, observe the scan tool LED Backlight Dimming parameter while operating the dimmer switch from low to high. The parameter should indicate between 5-50% when the dimmer switch is moved up and down.
• If the parameter does not change between the selected states, refer to Dimmer Switch Malfunction.
2. Command the LED Backlight Dimming Command ON and OFF with a scan tool. The LED backlighting components should turn ON and OFF when changing between the commanded states.
• If the LED backlighting components do not change between the commanded states, refer to Interior Backlighting Malfunction.
Circuit/System Testing
Dimmer Switch Malfunction
1. Ignition OFF, disconnect the harness connector at the S36 instrument panel dimmer switch.
2. Ignition OFF, test for less than 60 ohm between the low reference circuit terminal 10 and ground.
• If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the K9 BCM.
3. Ignition ON, test for B+ between the B+ circuit terminal 5 and ground.
• If less than the specified range, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K9 BCM.
Note: The BCM will automatically put in a default Incandescent Dimming Duty Cycle Command setting of 50%. The next step will look for a brief change in the Incandescent Dimming Duty Cycle Command parameter from 50% to 5% - returning after 3 seconds to the 50% default setting.
4. Install a 3 A fused jumper wire between the signal circuit terminal 9 and the B+ circuit terminal 5. Verify the scan tool Incandescent Dimming Duty Cycle Command briefly drops to 5%, returning after 3 seconds to the 50% default value.
• If less than the specified range, test the signal circuit for short to ground or an open/high resistance. If the circuit tests normal, replace the K9 BCM.
5. If all circuits test normal, test or replace the S36 instrument panel dimmer switch.
Interior Backlighting Malfunction
1. Ignition OFF, disconnect the harness connector at the inoperative backlighting component.
2. Ignition OFF, scan tool disconnected, interior lamps OFF, doors CLOSED, test for less than 5 ohm between the ground circuit and ground.
• If greater than the specified value, test the ground circuit for an open/high resistance.
3. Connect a test lamp between the control circuit and ground.
4. Command the LED Backlight Dimming Command ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
• 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 BCM.
• If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.
5. If all circuits test normal, replace the inoperative backlighting component.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Dimmer Switch Replacement (Service and Repair)
* Refer to the appropriate replacement procedure for the component causing the condition.
* Control Module References (Programming and Relearning) for BCM, HVAC, instrument panel cluster, or radio replacement, setup, and programming