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 instrument panel (I/P) dimmer switch is used to increase and decrease the brightness of the interior backlighting components. The I/P dimmer 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) provides a low reference signal and a B+ voltage reference to the I/P dimmer switch. When the I/P dimmer switch is placed in the desired position, the dimmed voltage setting is applied from the I/P dimmer switch through the I/P dimmer switch signal circuit to the BCM. The BCM interprets the signal and applies the dimmed voltage to the I/P lamps supply voltage circuit 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 Description and Operation)
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 Potentiometer parameter while operating the dimmer switch from low to high. The parameter should change from high to low when the dimmer switch is moved up and down.
• If the parameter does not change between the selected states, refer to Dimmer Switch Malfunction.
2. Observe the backlit dimming components while operating the dimmer switch from low to high. The brightness of the components should change as the dimmer switch is moved up and down.
• If the brightness of the LED backlighting components does not change as selected, refer to Interior Backlighting Malfunction.
Circuit/System Testing
Dimmer Switch Malfunction
1. Ignition OFF, disconnect the headlamp and panel dimmer switch connector.
2. Ignition OFF, verify that a test lamp illuminates between the low reference circuit terminal 3 and B+.
• 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 V.
• 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 3 A 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 V.
• 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 and panel dimmer 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 range, test the ground circuit for an open/high resistance.
3. Connect a test lamp between the control circuit and ground.
4. Command the Gauge 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 inoperative backlighting.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Refer to the appropriate replacement procedure for the component causing the condition.
* Headlamp Switch Replacement (Service and Repair)
* Control Module References (Programming and Relearning) for BCM module, replacement, setup, and programming