The body control module (BCM) is responsible for the dimming of the interior lights. The BCM receives a varying signal from the I/P dimmer switch. Based on the position of the I/P dimmer switch, the BCM then supplies the appropriate amount of voltage to the interior lamps. When the headlight switch is turned to the PARK or HEADLAMP position, all incandescent back lighting turns ON at the dimming level indicated by the I/P dimmer switch. 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 position.

Schematic Reference

Interior Lights Dimming 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

Ignition ON, command the Incandescent Dimming ON and OFF with a scan tool. The backlighting should change from high intensity to low intensity when commanded.

I/P Dimmer Switch Malfunction

1. Ignition OFF, disconnect the harness connector at the headlamp switch.
2. Verify that a test lamp illuminates between the low reference circuit terminal 7 and B+.

⇒	If the test lamp does not illuminate, test the low reference circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.

3. Ignition ON, test for 9.8-10.2 volts between the10-volt reference circuit terminal 2 and ground.

⇒	If less than the specified range, test the 10-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.

⇒	If greater than the specified range, test the 10-volt reference circuit for a short to voltage. If the circuit tests normal, replace the BCM.

4. Ignition ON, test for 9.8-10.2 volts between the10-volt reference circuit terminal 2 and the signal circuit terminal 1.

⇒	If less than the specified range, test the low reference circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.

5. Ignition ON, verify that a test lamp does not illuminate between the signal circuit terminal 1 and B+.

⇒	If the test lamp illuminates, test the signal circuit for a short to ground. If the circuit tests normal, replace the BCM.

6. If all circuits test normal, replace the headlamp switch.

Interior Backlighting Malfunction

1. Ignition OFF, disconnect the X1 harness connector at the BCM.
2. Verify that a test lamp illuminates between the B+ circuit terminal 52 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, connect the X1 harness connector at the BCM.
4. Ignition OFF, disconnect the harness connector at the component with the inoperative incandescent backlighting.
5. 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.

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 backlighting.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.