The body control module (BCM) applies battery voltage to the courtesy lamps through the courtesy lamps control circuit. When any door is opened, the door ajar switch contacts close and the BCM receives a door-open input. If the BCM receives a door lock or unlock input or a rear hatch open input, the BCM will activate the courtesy lamps control circuit, providing battery voltage to all of the dome lamps and reading lamps. The dome lamp switch consists of 3 positions, ON, DOOR, and OFF. When the dome lamp switch is placed in the DOOR position, the dome lamps will illuminate when a door is opened. The dome lamps are provided with battery voltage via the courtesy lamps control circuit and ground through the courtesy lamps low control circuit. In the event that any of these lamps were to remain illuminated for more than 20 minutes with the ignition switch in the OFF position, the BCM will deactivate the courtesy lamp high control circuit to prevent a total battery discharge condition.

Battery voltage must be between 9-16 volts.

DTC B2555 05 will set when the BCM detects a short to voltage or an open in the courtesy lamp low control circuit.

When the DTC is present, the dome lamps will not illuminate when a door is opened.

Schematic Reference

Interior Lights 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 OFF, disconnect the harness connector at the appropriate dome/inside rearview lamp assembly.
2. Connect a test lamp between B+ and the appropriate control circuit terminal listed below.

•	Dome lamp control terminal B

•	Inside rearview mirror courtesy/reading lamp control terminal 1 with UE1

•	Inside rearview mirror courtesy/reading lamp control terminal 6 without UE1

3. Command the Interior Lamps 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 voltage 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 ground. If the circuit tests normal, replace the BCM.

4. If all circuits test normal, replace the inoperative dome/inside rearview lamp assembly.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.