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 instrument panel (I/P) dimming 12 V reference circuit to the interior lamp 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 the I/P lamps dimmer switch signal circuit to the BCM. The BCM interprets this voltage signal, then applies a pulse width modulated (PWM) voltage through the instrument panel lamp control circuit, the backlight lamp control circuit, and the LED dimming control circuit illuminating the LED and I/P panel lamps.
Reference Information
Schematic Reference
Interior Lights Dimming Schematics Interior Lights Dimming Schematics
Connector End View Reference
Component Connector End Views A/C Compressor Clutch
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 Dimming Control Signal parameter while operating the dimmer switch from high to low. The reading should change from a high percent to a low percent as the switch is rotated.
• If the reading does not change, refer to Dimmer Switch Malfunction.
2. Command the Incandescent Dimming to change intensity with the scan tool. The appropriate incandescent lighting items should change in intensity.
• If any incandescent lighting items do not change in intensity, refer to Interior Backlighting Malfunction.
3. Command the LED Dimming to change intensity with the scan tool. The appropriate LED dimming items should change in intensity.
• If any LED lighting items do not change in intensity, refer to Interior Backlighting Malfunction.
Circuit/System Testing
Dimmer Switch Malfunction
1. Ignition OFF, disconnect the harness connector at the headlamp switch.
2. Ignition OFF, verify that a test lamp illuminates between the ground circuit terminal 8 and B+.
• If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
3. Ignition ON, test for 11.8-12.2 V between the 12 V reference circuit terminal 15 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 BCM.
• 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 BCM.
4. Ignition ON, verify the scan tool Dimming Control Signal parameter is less than 0.1 V.
• If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the BCM.
5. Install a 3 A fused jumper wire between the signal circuit terminal 13 and the voltage reference circuit terminal 15. Verify the scan tool Dimming Control Signal parameter is greater than 11.7 V.
• 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 BCM.
6. If all circuits test normal, test or replace the headlamp switch.
Interior Backlighting Malfunction
Note:
Each back lighted component may need to be disconnected to isolate a short to voltage or short to ground. Use the schematic to identify the following:
* Back lighted components the vehicle is equipped with.
* Component locations on the back lighting dimming 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 ohms 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 terminal and ground.
4. Command the Incandescent Dimming or LED 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 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, test or replace the component with the inoperative backlighting.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Headlamp Switch Replacement Service and Repair
* Refer to the appropriate replacement procedure for the lighting component that requires replacement.
* Control Module References Programming and Relearning for BCM, HVAC, IPC, or Radio replacement, programming and setup