Circuit/System Testing

Dimmer Switch Malfunction

1. Ignition OFF, disconnect the harness connector at the headlamp switch.
2. Ignition OFF, 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 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 switch.

Interior Backlighting Malfunction

1. Ignition OFF, disconnect the harness connector at the component with the inoperative backlighting.
2. Test for less than 5 ohms between the appropriate ground circuit terminal listed below and ground.
   • Headlamp Switch terminal 8
   • Hazard Switch terminal B
   • Ashtray Lamp terminal B
   • HVAC Control Module terminal 11 X1
   • Driver Information Display Switch terminal 6
   • Clock terminal 2
   • Radio terminal 8 X1
   • Left Middle Door Window Switch terminal 1 - Limo
   • Right Middle Door Window Switch terminal 1 - Limo
   • Traction Control Switch terminal A
   • Floor Shifter Assembly terminal D X2
   • Garage Door Opener Transmitter terminal 3
   • Sunshade Switch terminal A
   • Sunroof Switch terminal 5
   • Left Rear Door Window Switch terminal 1
   • Left Rear Heated Seat Switch terminal J
   • Left Rear Seat Lumbar Switch terminal E
   • Right Rear Door Window Switch terminal 1
   • Right Rear Heated Seat Switch terminal J
   • Right Rear Seat Lumbar Switch terminal E
   • Auxiliary HVAC Control Module terminal 8
   • Right Steering Wheel Control Switch terminal 1
   • Left Steering Wheel Control Switch terminal 8
   • If greater than the specified range, test the ground circuit for an open/high resistance.
3. Connect a test lamp between the appropriate control circuit terminal listed below and ground.

   Incandescent Dimming

   • Hazard Switch terminal A
   • Ashtray Lamp terminal A
   • Traction Control Switch terminal D
   • Floor Shifter Assembly terminal C X2
   • Garage Door Opener Transmitter terminal 2
   • Sunshade Switch terminal D
   • Sunroof Switch terminal 3
   • Left Rear Door Window Switch terminal 2
   • Left Rear Heated Seat Switch terminal F
   • Left Rear Seat Lumbar Switch terminal D
   • Right Rear Door Window Switch terminal 2
   • Right Rear Heated Seat Switch terminal F
   • Right Rear Seat Lumbar Switch terminal D
   • Left Middle Door Window Switch terminal 2 - Limo
   • Right Middle Door Window Switch terminal 2 - Limo

   LED Dimming

   • Headlamp Switch terminal 7
   • HVAC Control Module terminal 2 X3
   • Driver Information Display Switch terminal 5
   • Clock terminal 3
   • Radio terminal 7 X1
   • Auxiliary HVAC Control Module terminal 10
   • Right Steering Wheel Control Switch terminal 2
   • Left Steering Wheel Control 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 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 the inoperative backlighting.

Front Door Switch Backlighting Malfunction

1. Ignition OFF, disconnect the X4 harness connector at the appropriate driver or front passenger door control module.
2. Connect a 3A fused jumper wire between the low reference circuit terminal 4 and ground.
3. Connect a test lamp between the control circuit terminal 13 and B+. The heated and cooled seat switch backlighting should illuminate.
   • If the switch backlighting does not illuminate, replace the heated and cooled seat switch.
4. If the switch backlighting tests normal, replace the door control module.