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 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 resistor ladder 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.
* Dome/reading lamps
* Sunroof switch
* Sunroof sunshade switch
* Outside rearview mirror switch
* Window switches
* Headlamp switch
* Park brake control switch
* Head-up display switch
* Ignition mode switch
* Multifunction switch 1 - instrument panel
* Multifunction switch 2 - instrument panel
* Steering wheel controls switches
* Garage door opener
Reference Information
Schematic Reference
* Interior Lights Schematics (Interior Lights Schematics)
* Interior Lights Dimming Schematics (Interior Lights Dimming Schematics)
* Object Detection Schematics ([1][2]Collision Avoidance and Parking Assist Systems)
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 Indicator Dimming Duty Cycle Command parameter while operating the dimmer switch from high to low. The reading should change from a high percentage to a low percentage.
• If the reading does not change, refer to Dimmer Switch Malfunction.
2. Observe the backlighting component while commanding the LED Backlight Dimming ON and OFF with the scan tool. The backlighting component should turn ON and OFF when changing between the commanded states.
• If the backlighting does not go ON and OFF, refer to Interior Backlighting Malfunction
Circuit/System Testing
Dimmer Switch Malfunction
1. Ignition OFF, disconnect the harness connector at the S30 headlamp switch.
2. Test for less that 10 Ohms between the ground circuit terminal 6 and ground.
• If greater than the specified range, test the ground circuit for an open high/resistance.
3. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 1 and ground.
• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K9 BCM.
4. Ignition ON, test for less than 0.3 V between signal circuit terminal 12 and ground.
• If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the K9 BCM.
5. Install a 3 A fused jumper wire between the signal circuit terminal 12 and the B+ circuit terminal 1. The interior backlighting should 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 BCM.
6. If all circuits test normal, test or replace the S30 headlamp switch.
Interior Backlighting Malfunction
Note: Each LED backlight may need to be disconnected to isolate the short to ground. Use the schematic to identify the following:
* All LED backlight equipped with the vehicle
* Component locations on the LED backlight control circuit
* Each component's control circuit terminals
1. Ignition OFF, disconnect the harness connector at the appropriate backlighting component.
2. Test for less than 30 ohm between the ground circuit terminal and ground.
• If greater than the specified range, test the ground circuit terminal for an open/high resistance.
3. Connect a test lamp between the control circuit and ground
4. Command the LED Backlight Dimming 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 K9 BCM.
• If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the K9 BCM.
5. If all circuits test normal, test or replace the LED backlighting component.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Dome and Reading Lamp Replacement - Front (Dome and Reading Lamp Replacement - Front)
* Dome and Reading Lamp Replacement - Rear (Dome and Reading Lamp Replacement - Rear)
* Sunroof Switch Replacement (Service and Repair)
* Outside Remote Control Rearview Mirror Switch Replacement (Service and Repair)
* Front Side Door Window and Multifunction Switch Replacement (Front Side Door Window and Multifunction Switch Replacement)
* Rear Side Door Window Switch Replacement (Rear Side Door Window Switch Replacement)
* Headlamp Switch Replacement (Service and Repair)
* Parking Brake Switch Replacement (Service and Repair)
* Instrument Panel Multifunction Switch Replacement (Service and Repair)
* Accessory Switch Replacement (Service and Repair)
* Radio and Telephone Control Switch Replacement (Radio and Telephone Control Switch Replacement)
* Cruise Control Switch Replacement (Service and Repair)
* Control Module References (Programming and Relearning) for BCM, HVAC, instrument panel cluster, or radio replacement, setup, and programming