Operation CHARM: Car repair manuals for everyone.
Home >> GMC Truck >> 2009 >> Sierra 2500 2WD V8-6.6L DSL Turbo >> Repair and Diagnosis >> Lighting and Horns >> Testing and Inspection >> Symptom Related Diagnostic Procedures >> Interior Backlighting Malfunction (w/AN3)

Interior Backlighting Malfunction (w/AN3)



Interior Backlighting Malfunction (w/AN3)

Diagnostic Instructions

* Perform theDiagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* ReviewStrategy 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.



Diagnostic Fault Information






Circuit/System Description

When the ignition switch is turned to the RUN position, the radio VF display turns ON at maximum brightness. When the park lamps are ON, all incandescent and LED back lighting turn ON at the dimming level indicated by the instrument panel (I/P) dimmer switch. At the same time all VF displays dim to match the indicated dimming level. The panel dimmer switch potentiometer is an input to the body control module (BCM). When the driver selects a dimming setting by moving the I/P dimming switch potentiometer, all 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 incandescent back lighting respond from minimum intensity to maximum brightness in response to the I/P dimmer switch


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. Ignition ON, observe the driver door switch while commanding the Driver Door Switch Integrated Sw. Backlighting Test ON and OFF with a scan tool. The switch backlighting should turn ON and OFF between commanded states.

• If the backlighting does not turn On and OFF or remains always ON, replace the driver door lock and side window switch.

2. Ignition ON, observe the driver memory/heated seat switch while commanding the Driver Door Switch Non-Integrated Sw. Backlighting Test ON and OFF with a scan tool. The switch backlighting should turn ON and OFF between commanded states.

• If the backlighting does not turn On and OFF or remains always ON, refer to Front Door Switch Backlighting Circuit Test.

3. Ignition ON, observe the passenger door switch while commanding the Passenger Door Switch Integrated Sw. Backlighting Test ON and OFF with a scan tool. The switch backlighting should turn ON and OFF between commanded states.

• If the backlighting does not turn On and OFF or always remains ON, replace the passenger door lock and side window switch.

4. Ignition ON, observe the passenger heated seat switch while commanding the Passenger Door Switch Non-Integrated Sw. Backlighting Test ON and OFF with a scan tool. The switch backlighting should turn ON and OFF between commanded states.

• If the backlighting does not turn On and OFF or remains always ON, refer to Front Door Switch Backlighting Circuit Test.

5. 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 the Interior Backlighting Circuit Test or the LED Dimming Circuit Test.




Circuit/System Testing


Interior Backlighting Malfunction - Incandescent
1. Ignition OFF, disconnect the X3 harness connector at the BCM.
2. Ignition ON, verify a test lamp illuminates between the IS LPS fuse B+ circuit terminal 2 and ground.

• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.

3. Ignition OFF, reconnect the X3 harness connector at the BCM.
4. Disconnect the harness connector at the component with the inoperative incandescent backlighting.
5. Ignition OFF, scan tool OFF, 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.

6. Connect a test lamp between the control circuit and ground.
7. Command the Incandescent Dimming Control 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.

8. If all circuits test normal, test or replace the component with the inoperative incandescent backlighting.



Dimmer Switch Malfunction
1. Ignition OFF, disconnect the harness connector at the headlamp and panel dimmer switch.
2. 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, verify the scan tool Dimming Control Signal parameter is less than 0.1 volts.

• If greater than the specified range, test the signal circuit terminal 13 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 15 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 13 and the voltage reference circuit terminal 15. 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 headlamp and panel dimmer switch.



Interior Backlighting Malfunction
1. Ignition OFF, disconnect the harness connector at the appropriate component.
2. Verify that a test lamp illuminates between the listed ground circuit terminal and B+.

* Rear Window Switch terminal F
* Headlamp and Panel Dimmer Switch terminal 8
* Transfer Case Shift Control Switch terminal 6
* Sunroof Switch terminal 5
* Roof Beacon Switch terminal 1
* Sliding Rear Window Switch terminal D
* Garage Door Opener Switch terminal 3
* Door Lock Switch terminal B
* Window Switch terminal F
* Outside Rearview Mirror Switch terminal G


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

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

* Rear window switch terminal B
* Headlamp switch terminal 7
* Transfer case control switch terminal 5
* Sunroof switch terminal 3
* Roof beacon switch terminal 2
* Sliding rear window switch terminal E
* Garage door opener switch terminal 2
* Door Lock Switch terminal A
* Window Switch terminal B
* Outside Rearview Mirror Switch terminal E

4. Command the Incandescent Dimming Test ON with a scan tool. The test lamp should turn from bright to dim 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 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 appropriate component.



LED Dimming Circuit Test
1. Ignition OFF, disconnect the harness connector at the appropriate component.
2. Verify that a test lamp illuminates between the listed ground circuit terminal and battery voltage.

* Right steering wheel switch terminal 1
* Left steering wheel switch terminal 8
* DIC switch terminal 5
* Manual HVAC control module terminal 10 X2
* Multifunction accessory switch terminal 3


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

3. Connect a test lamp between the listed LED dimming control circuit terminal and ground.

* Right steering wheel switch terminal 2
* Left steering wheel switch terminal 6
* Power take off switch terminal 6
* Trailer brake controller switch terminal 7
* IPC terminal 8
* Radio terminal 7 X1
* DIC switch terminal 4
* Manual HVAC control module terminal 1 X2
* Multifunction accessory switch terminal 4

4. Command the dimming test high to low with a scan tool. The test lamp should turn from bright to dim when changing between the commanded states.

• 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 appropriate component.



Front Door Switch Backlighting Circuit Test
1. Ignition OFF, disconnect the harness connector X4 at the door lock and side window switch.
2. Connect a 3A fused jumper wire between the low reference circuit terminal 4 and ground.
3. Connect a test lamp between the backlight supply voltage circuit terminal 13 and B+. The heated seat switch backlighting should illuminate.

• If the switch backlighting does not illuminate, replace the heated seat switch.

4. If the switch backlighting tests normal, replace the door lock and side window switch.



Repair Instructions

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

* Front Seat Heater Switch Replacement (Front Seat Heater Switch Replacement)
* Steering Wheel Control Switch Assembly Replacement (Service and Repair)
* Driver Information Display Switch Replacement (with RPO SLT) (Driver Information Display Switch Replacement (with RPO SLT))Driver Information Display Switch Replacement (without RPO SLT) (Driver Information Display Switch Replacement (without RPO SLT))
* Accessory Switch Replacement (with RPO SLT) (Accessory Switch Replacement (with RPO SLT))Accessory Switch Replacement (without RPO SLT) (Accessory Switch Replacement (without RPO SLT))
* Headlamp Switch Replacement (with RPO SLT) (Headlamp Switch Replacement (with RPO SLT))Headlamp Switch Replacement (without RPO SLT) (Headlamp Switch Replacement (without RPO SLT))
* Control Module References (Programming and Relearning) for BCM, door lock and side window switch, IPC, radio, HVAC control module, and rear seat audio controller replacement, programming, and setup.


pro multis · About Operation CHARM