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 through the dimmer switch, which is part of the headlamp switch. When the dimmer switch is placed in a desired brightness position, reference voltage is applied through the dimmer switch rheostat and through the dimmer switch signal circuit 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 instrument panel cluster lamps.
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)
Circuit/System Verification
1. Ignition ON, observe the scan tool Indicator LED Backlight Dimming Command parameter while operating the dimmer switch from high to low. The parameter should indicate between 5-50% 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. Test for less than 5 ohm between the ground circuit harness connector terminal 6 and ground.
• If greater than the specified value, test the ground circuit for an open/high resistance.
3. Ignition ON, connect a test lamp between the 12 V reference circuit terminal 1 and ground.
• If the test lamp is always OFF, 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.
4. 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.
5. Ignition OFF, reconnect the harness connector to the S30 Headlamp Switch.
6. Ignition ON, put the S30 Headlamp Switch in the park lamps position and set the interior to maximum dim.
7. Disconnect the harness connector at the S30 Headlamp Switch.
8. 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.
9. If all circuits test normal, test or replace the S30 Headlamp Switch.
Interior Backlighting Circuit Test
1. Ignition OFF, disconnect the harness connector at the appropriate inoperative backlighting component.
2. Disconnect the negative terminal of the C1 Battery.
3. Test for less than 5 ohm between the ground circuit terminal black wire and ground.
• If greater than the specified range, test the ground circuit for an open/high resistance.
4. Reconnect the negative terminal to the C1 Battery.
5. Connect a test lamp between the control circuit terminal yellow wire and ground.
6. Ignition ON, command the LED Backlight Dimming test 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 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.
7. If all circuits test normal, test or replace the appropriate component with the inoperative backlighting.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests)
* Sunroof Switch Replacement (Service and Repair)
* Outside Remote Control Rearview Mirror Switch Replacement (Service and Repair)
* Rear Side Door Window Switch Replacement (Rear Side Door Window Switch Replacement)
* Steering Wheel Inflatable Restraint Module Replacement (Steering Wheel Inflatable Restraint Module Replacement)
* Headlamp Switch Replacement (Service and Repair)
* Parking Brake Indicator Switch Replacement (Service and Repair)
* Hazard Warning Switch Replacement (Service and Repair)
* Body Control Module Replacement (Body Control Module Replacement)
* Steering Wheel Inflatable Restraint Module Replacement (Steering Wheel Inflatable Restraint Module Replacement)
* Control Module References (Programming and Relearning)