Interior Backlighting Malfunction
Interior Backlighting Malfunction
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* 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 voltage reference circuit to the interior lamp dimmer 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 supply voltage circuit and the indicator dimming control circuit illuminating the LED and I/P panel lamps. For more detailed information concerning interior lamp operation refer to Interior Lighting Systems Description and Operation.
Circuit/System Verification
Ignition ON, observe the scan tool BCM 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 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 harness connector at the dimmer switch.
2. Ignition OFF, verify that a test lamp illuminates between the ground circuit terminal C and B+.
• If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
3. Ignition ON, verify the scan tool BCM Dimming Control Signal parameter is less than 0.1 volts.
• If greater than the specified range, test the signal circuit terminal B for a short to voltage. If the circuit tests normal, replace the BCM.
4. Ignition ON, test for B+ between the I/P dimming voltage reference circuit terminal D and ground.
• If less than the specified value, test the voltage reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
5. Install a 3A fused jumper wire between the signal circuit terminal B and the voltage reference circuit terminal D. Verify the scan tool BCM Dimming Control Signal parameter is greater than 2.6 volts.
• 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 dimmer switch.
Interior Backlighting Circuit Test
1. Ignition OFF, disconnect the harness connector at the component with the inoperative backlighting.
2. Test for less than 5.0 ohms of resistance between the appropriate component ground circuit terminal listed below and ground.
* Hazard Switch - terminal J
* HVAC Control Module - terminal 10
* Radio - terminal 8 X1
* Driver Information Center - terminal 5
* Traction Control Switch - terminal 2
* Steering Wheel Control Switches - terminal 1
* Power window switch - terminal 6
* Rear wiper/washer/fog lamp switch - terminal 5
• If greater than the specified range, test the ground circuit for an open/high resistance.
3. Connect a test lamp between the appropriate component supply voltage circuit terminal listed below and ground.
* Hazard Switch - terminal I
* HVAC Control Module - terminal 1
* Radio - terminal 7 X1
* Driver Information Center - terminal 4
* Traction Control Switch - terminal 3
* Left Steering Wheel Control Switch - terminal 6
* Right Steering Wheel Control Switch - terminal 2
* Power window switch - terminal 2
* Rear wiper/washer/fog lamp switch - terminal 6
4. Ignition ON, command the appropriate 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 supply voltage 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 supply voltage 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 after completing the diagnostic procedure. Verification Tests
* Hazard Warning Switch Replacement
* Front Side Door Window Switch Replacement
* Instrument Panel Lamp Dimmer Switch Replacement
* Radio Replacement
* Hazard Warning Switch Replacement
* Fog Lamp Switch Replacement
* Driver Information Display Switch Replacement
* Steering Wheel Replacement