The CTSY/RF TRN fuse supplies battery voltage to the body control module (BCM). When the BCM commands the courtesy lamps ON, it applies battery voltage through the courtesy lamp relay control circuit to the coil side of the OVRHD LAMPS Relay, energizing the relay. Battery voltage from the inadvertent power courtesy lamp circuit is applied through the switch side of the relay and the courtesy lamp supply voltage circuit to the overhead console lamp, illuminating the courtesy lamp. The BCM also applies battery voltage through the courtesy lamp supply voltage circuit to the left and right roof rail courtesy lamps and the front, middle, and rear door courtesy lamps. When any door is opened, the door open switch contacts close and the BCM receives a door-open input and it will illuminate the courtesy lamps. If the BCM receives a door lock or unlock input or a rear hatch open input, it will illuminate the courtesy lamps.

Battery voltage must be between 9-16 volts.

The BCM detects a short to voltage in the courtesy lamp relay control circuit.

The BCM will deactivate the overhead lamps relay for the remainder of the ignition cycle.

Schematic Reference

Interior Lights Schematics

Connector End View Reference

Lighting Systems Connector End Views

Electrical Information Reference

Scan Tool Reference

1. Ignition OFF, remove the OVRHD LAMPS Relay from the rear fuse block.
2. Connect a test lamp between the control circuit terminal 4 and ground.
3. Ignition ON, command the Courtesy Lamp 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 ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.

⇒	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.

4. If the circuit tests normal, test or replace the overhead lamp relay.

Relay Test

1. Ignition OFF, disconnect the relay.
2. Test for 70-100 ohms of resistance between terminals 85 and 86.

⇒	If the resistance is not within the specified range, replace the relay.

3. Test for infinite resistance between the following terminals:

•

30 and 85

•

30 and 86

•

30 and 87

•

85 and 87

⇒	If not the specified value, replace the relay.

4. Install a 10A fused jumper wire between relay terminal 85 and B+. Install a jumper wire between relay terminal 86 and ground. Test for less than 2 ohms of resistance between terminals 30 and 87.

⇒	If greater than the specified range, replace the relay.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.