The instrument panel (I/P) lamp 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. The BCM also sends a serial data message to the driver and front passenger door modules indicating the dimmed level. The door modules respond by supplying there respective switch backlighting with the appropriate voltage for the desired dimmed setting.

Schematic Reference

Interior Lights Dimming Schematics

Driver Seat Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Interior Lighting Systems Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

1. Ignition ON, observe the scan tool 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 activated.

⇒	If the reading does not change, refer to I/P Dimmer Switch Malfunction.

2. With a scan tool, perform the Integrated Sw. Backlighting Test for the driver door switch. The driver door switch backlighting should illuminate from high to low.

⇒	If the driver door switch backlighting does not operate as described, replace the driver door module (DDM).

3. With a scan tool, perform the Integrated Sw. Backlighting Test for the passenger door switch. The passenger door switch backlighting should illuminate from high to low.

⇒	If the passenger door switch backlighting does not operate as described, replace the driver door module (PDM).

4. With a scan tool, perform the Non-Integrated Backlighting Test for the driver door switch. The memory switch backlighting should turn ON and OFF.

⇒	If the memory switch backlighting does not operate as described, refer to Memory Switch Indicator Malfunction.

I/P Dimmer Switch Malfunction

1. Ignition OFF, disconnect the harness connector at the I/P Dimmer switch.
2. Ignition OFF, verify that a test lamp illuminates between B+ and the ground circuit terminal 10.

⇒	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 9 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 5 and ground.

⇒	If less than the specified range, test the B+ 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 9 and the B+ reference circuit terminal 5. Verify the scan tool Dimming Control Signal parameter is greater than 2.5 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 I/P dimmer switch.

Interior Backlighting Malfunction - Incandescent

1. Ignition OFF, disconnect the harness connector at the component with the inoperative incandescent backlighting.
2. Ignition OFF, 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.

3. Connect a test lamp between the control circuit and ground.
4. 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.

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

Interior Backlighting Malfunction - LED

1. Ignition OFF, disconnect the X3 harness connector at the BCM.
2. Ignition ON, verify that a test lamp illuminates between the BCM 2 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 LED 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 LED 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 LED backlighting.

Memory Switch Indicator Malfunction

1. Ignition OFF, disconnect the X4 harness connector at the driver door module.
2. Connect a test lamp between the control circuit terminal 13 and the low reference circuit terminal 4 at the drive door module terminal pins.
3. Command the Non-Integrated Backlighting Test 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 does not turn ON and OFF when commanded, replace the driver door module.

4. If all circuits test normal, replace the memory switch.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.