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

The body control module (BCM) is responsible for the dimming of the interior lights. The BCM receives a varying signal from the I/P dimmer switch. Based on the position of the I/P dimmer switch, the BCM then supplies the appropriate amount of voltage to the interior lamps. When the headlight switch is turned to the PARK or HEADLAMP position, all incandescent back lighting turns ON at the dimming level indicated by the I/P dimmer switch. When the I/P dimmer switch is moved from MIN to MAX, all VF displays, as well as all incandescent back lighting, respond from minimum intensity to maximum brightness in response to the I/P dimmer switch position.


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 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

1. Place the headlamp switch in the PARK position. The interior backlighting should illuminate.

• If the interior backlighting does not illuminate, refer to Interior Backlighting Inoperative.

2. Operate the interior backlighting dimmer switch. The interior backlighting intensity should vary with the position of the switch.

• If the backlighting intensity does not vary, refer to Interior Backlighting Does Not Dim.




Circuit/System Testing


Interior Backlighting Inoperative
1. Ignition OFF, disconnect the harness connector at the dimmer switch.
2. Install a 3A fused jumper wire between the signal circuit terminal C and ground.
3. Ignition ON, headlamp switch in the PARK position. The interior backlighting should illuminate.

• If the interior backlighting does not illuminate, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.

4. Install a 3A fused jumper wire between the signal circuit terminal C and the low reference circuit terminal D. The interior backlighting should illuminate.

• If the interior backlighting does not illuminate, test the low reference circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.

5. If all circuits test normal, replace the dimmer switch.



Interior Backlighting Does Not Dim
1. Ignition OFF, disconnect the dimmer switch.
2. Ignition ON, headlamp switch in the PARK position. The interior backlighting should not illuminate.

• If the interior backlighting illuminates, test the signal circuit terminal C for a short to ground. If the circuit tests normal, replace the BCM.

3. If all circuits test normal, replace the dimmer switch.



Repair Instructions

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

* Instrument Panel Lamp Dimmer Switch Replacement (Service and Repair)
* Control Module References (Programming and Relearning) for BCM replacement, setup, and programming