The instrument panel cluster (IPC) receives an input from the dimmer/heads up display (HUD) switch. The IPC provides the dimmer/HUD switch with battery positive voltage and ground. The dimmer/HUD switch is a potentiometer that varies the input signal voltage to the IPC. This input determines the intensity level of the backlighting illumination. The driver may change intensity of the backlighting by positioning the dimmer/HUD switch between the minimum and maximum settings. The IPC will default to full intensity if the input from the dimmer/HUD switch is not within the specified values. The backlighting illumination intensity is controlled by the IPC by varying the pulse width modulation (PWM) voltage that feeds the dimming signal circuits of the individual lamps. All interior backlighting lamps are permanently grounded.

Schematic Reference

Interior Lights Dimming Schematics

Connector End View Reference

Lighting Systems Connector End Views

Electrical Information Reference

Scan Tool Reference

1. Ignition ON, observe the scan tool Dim Select Switch parameter while pressing and releasing the dimmer switch. The reading should toggle between ACTIVE and INACTIVE.

⇒	If the reading does not change between the commanded states, refer to Dimmer Switch Malfunction.

2. Observe the scan tool dim down switch parameter while pressing and releasing the dim down switch. The reading should toggle between ACTIVE and INACTIVE.

⇒	If the reading does not change between the commanded states, refer to Dimmer Switch Malfunction.

3. Observe the scan tool Dim Up Switch parameter while pressing and releasing the dim up switch. The reading should toggle between ACTIVE and INACTIVE.

⇒	If the reading does not change between the commanded states, refer to Dimmer Switch Malfunction.

4. If the dimmer switch functions as specified, refer to Interior Backlighting Malfunction.

Interior Backlighting Malfunction

1. Ignition ON, install a scan tool and observe the park lamps signal parameter in the IPC data list while turning the parks lamps ON and OFF. The reading should change between OFF and ON.

⇒	If the parameter is always ON, test the park lamp supply voltage circuit at connector C1 terminal A16 for a short to voltage. If the circuit tests normal, replace the IPC.

⇒	If the parameter is always OFF, test the park lamp supply voltage circuit at connector C1 terminal A16 for a short to ground or and open/high resistance. If the circuit tests normal, replace the IPC.

2. Ignition OFF, disconnect the harness connector at the component with the inoperative backlighting.
3. Test for less than 1 ohm of resistance between the ground circuit and ground.

⇒	If greater than the specified range, test the ground circuit for an open/high resistance.

4. Connect a test lamp between the backlight lamp control circuit and ground.
5. Command the park lamps ON and OFF with the park lamps switch. 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 control module associated with the inoperative backlight.

⇒	If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the control module associated with the inoperative backlight.

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

Dimmer Switch Malfunction

1. Ignition OFF, disconnect the harness connector at the dimmer/head up display (HUD) switch.
2. Test for less than 1 ohm of resistance between the ground circuit terminal 1 and ground.

⇒	If greater than the specified range, test the ground circuit for an open/high resistance. If the circuit tests normal, replace the IPC.

3. Ignition ON, verify the scan tool dim select switch parameter is INACTIVE.

⇒	If not the specified value, test the signal circuit terminal 4 for a short to ground. If the circuit tests normal, replace the IPC.

4. Install a 3A fused jumper wire between the signal circuit terminal 4 and ground. Verify the scan tool Dim Select Switch parameter is ACTIVE.

⇒	If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the IPC.

5. Verify the scan tool Dim Down Switch parameter is INACTIVE.

⇒	If not the specified value, test the signal circuit terminal 3 for a short to ground. If the circuit tests normal, replace the IPC.

6. Install a 3A fused jumper wire between the signal circuit terminal 3 and ground. Verify the scan tool dim down switch parameter is ACTIVE.

⇒	If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the IPC.

7. Verify the scan tool Dim Up Switch parameter is INACTIVE.

⇒	If not the specified value, test the signal circuit terminal 2 for a short to ground. If the circuit tests normal, replace the IPC.

8. Install a 3A fused jumper wire between the signal circuit terminal 2 and ground. Verify the scan tool dim up switch parameter is ACTIVE.

⇒	If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the IPC.

9. If all circuits test normal, test or replace the dimmer/head up display (HUD) switch.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.