Interior Backlighting Malfunction

Interior Backlighting Malfunction

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.

Circuit/System Description

When the ignition switch is turned to the RUN position, the radio VF displays turn ON at maximum brightness. When the park lamps are ON, all dimmable incandescent back lighting illuminate at the dimming level indicated by the I/P dimmer switch and all the other back lighting lamps illuminate at full intensity. At the same time all VF displays dim to match the indicated dimming level. The panel dimmer switch potentiometer is an input to the BCM. When the driver selects a dimming setting by moving the I/P dimming switch potentiometer, all dimmable incandescent back lighting lamps are provided with a specific voltage. When the I/P dimmer switch is moved from MIN to MAX, all VF displays, as well as all dimmable incandescent back lighting respond from minimum intensity to maximum brightness in response to the I/P dimmer switch The grounding for all of the incandescent back lighting lamps is provided by G106.

Reference Information
Schematic Reference

Interior Lights Dimming Schematics (Interior Lights Dimming Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Interior Lighting Systems Description and Operation (Interior Lighting Systems Description and Operation)
Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information

Circuit/System Verification

Ignition ON, observe the scan tool Dimming Potentiometer parameter while operating the dimmer switch from high to low. The voltage reading should change from high to low as the switch is rotated.

If the reading does not change, refer to Dimmer Switch Circuit Test.

If the scan tool dimmer control operates normal, refer to Interior Backlighting Circuit Test.

Circuit/System Testing

Dimmer Switch Circuit Test
1. Ignition OFF, disconnect the headlamp switch connector.
2. Ignition OFF, verify that a test lamp illuminates between the low reference circuit terminal 3 and battery voltage.

• If the test lamp does not illuminate, test the low reference circuit for an open/high resistance.

3. Ignition ON, verify that the scan tool dimming potentiometer parameter displays greater than 4 volts.

• If the parameter displays less than the specified value, test the switch signal circuit for a short to ground. If the circuit tests normal replace the BCM.

4. Install a 3A fused jumper wire between the signal circuit terminal 14 and the low reference circuit terminal 3. Verify the scan tool dimming potentiometer parameter displays less than 1 volt.

• If the parameter displays greater than the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.

5. If the circuits test normal test or replace the headlamp switch.

Interior Backlighting Circuit Test
1. Ignition OFF, disconnect the harness connector at the affected component.
2. Ignition OFF, verify that a test lamp illuminates between the affected component ground circuit terminal and battery voltage.

* HVAC control module X1 terminal 14
* Hazard switch terminal B
* Accessory switch terminal H

• If the test lamp does not illuminate, test the ground circuit for an open/high resistance.

3. Connect a test lamp between the affected component backlighting control circuit terminal and ground.

* HVAC control module X1 terminal 14
* Hazard switch terminal A
* Accessory switch terminal G

4. Ignition ON and parklamps ON, operate the dimmer switch from high to low. The test lamp should illuminate bright to dim when rotating the dimmer switch.

• If the test lamp is always off, test the control circuit for an open/high resistance or short to ground. If the circuit tests normal, replace the BCM.

• If the test lamp is always bright, 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 affected component.

Component Testing

Dimmer Switch Test
1. Ignition OFF, disconnect the harness connector at the headlamp switch.
2. Test for 0.0 to 5.0K ohms between the signal terminal 14 and the low reference terminal 3 while rotating the dimmer switch from high to low.

• If not the specified value, replace the headlamp switch.

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Headlamp Switch Replacement (Service and Repair)
* Hazard Warning Switch Replacement (Service and Repair)
* Accessory Switch Replacement (Service and Repair)
* Control Module References (Programming and Relearning) for BCM, or HVAC module, replacement, setup, and programming