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 up/down dimmer controls located on the headlamp and panel dimmer switch is used to increase and decrease the brightness of the interior backlighting components. Each dimmer control switch provides a voltage signal that will increase as the brightness of the lights are increased and decrease as the brightness of the lights are decreased. The body control module (BCM) supplies each dimmer control switch with a signal circuit. When either the up or down dimmer control switch is placed in the desired position, the dimmed voltage setting is applied from the appropriate dimmer control switch through the dimmer switch signal circuit to the BCM. The BCM interprets the signal and applies the dimmed voltage to the LED and incandescent backlight dimming control circuits and the interior backlighting components dim to the requested level.
Reference Information
Schematic Reference
Interior Lights Dimming Schematics (Interior Lights Dimming Schematics)
Connector End View Reference
Component Connector End Views (Connector Views)
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, command the Parking Lamps ON and OFF with a scan tool. The park lamps should turn ON and OFF when changing between the commanded states.
• If the park lamps do not turn ON and OFF when commanded, refer to Park, License, and/or Tail Lamps Malfunction (Park, License, and/or Tail Lamps Malfunction).
2. Observe the scan tool LED Backlight Dimming Command parameter while operating the dimmer switch from high to low. The parameters should change from a high percent to a low percent as the switch is activated.
• If the parameters do not change, refer to Panel Dimmer Switch Malfunction.
3. Observe the function for the backlights while commanding the LED Dimming Duty Cycle Command ON and OFF with a scan tool. All backlights should turn ON and OFF while changing between the commanded states.
• If a backlight does not turn ON or OFF, refer to Interior Backlighting Malfunction.
Circuit/System Testing
Panel Dimmer Switch Malfunction
1. Ignition OFF, disconnect the harness connector at the S30 headlamp switch.
2. Ignition OFF, RAP OFF, scan tool disconnected, test for less than 5 ohm between the low reference circuit terminal 12 and ground.
• If greater than the specified value, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the K9 BCM.
3. Ignition ON, park lamps ON, test for greater than 10 V between the B+ circuit terminal 1 and ground.
• If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K9 BCM.
4. Install a 3 A fused jumper wire between the B+ circuit terminal 1 and the low reference circuit terminal 12. Verify the scan tool Dimming Control Signal parameter is a high %.
• If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K9 BCM.
5. If all circuits test normal, test or replace the S30 headlamp switch.
Interior Backlighting Malfunction
Note: Each interior backlighting component may need to be disconnected to isolate a short to voltage or short to ground. Use the schematic to identify the following:
* Backlighting components the vehicle is equipped with.
* Component locations on the backlighting control circuit
* Each component's control and ground circuit terminals
1. Ignition OFF, disconnect the harness connector at any component with inoperative backlighting.
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 Dimming Duty Cycle 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 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 component with inoperative backlighting.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Headlamp, Instrument Panel Lamp Dimmer, and Fog Lamp 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 replacement, setup and programming