The body control module (BCM) receives battery voltage from the CTSY/RF TRN fuse in order to supply power to the courtesy lamps. The BCM applies this voltage to the courtesy lamps through the courtesy lamp supply voltage circuits. When any door is opened, the door open switch contacts close and the BCM receives a door-open signal. If the BCM receives a door lock or unlock signal, the BCM will activate the courtesy lamp supply voltage circuit, providing battery voltage to the dome lamps. The BCM also sends a serial data message to the front door control modules to illuminate the door courtesy lamps. The courtesy lamps can be manually activated by placing the interior lamp switch in the DOME position. For more detailed information concerning courtesy lamp operation refer to Interior Lighting Systems Description and Operation.

The BCM receives battery voltage from the INT LAMPS fuse in order to supply power to the inadvertent courtesy lamps. Inadvertent power courtesy lamp feature provides a similar function for the interior lamps as a retained accessory power feature. The BCM will energize the courtesy lamps supply voltage circuit when the BCM is in the active state (awake). When the inadvertent power courtesy lamps supply voltage circuit is energized, it supplies voltage to all the interior lights listed below. The BCM will continue to supply voltage to the interior lamps after the ignition is turned OFF so that the interior lamps may be operated.

In the event that any of these lamps were to remain illuminated for a period of more than 20 minutes with the ignition switch in the OFF position and no BCM input activity, the BCM will deactivate the inadvertent power supply voltage circuit to prevent a total battery discharge condition.

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 ON, observe the scan tool Driver Door Open Sw. parameter while opening and closing the driver door. The parameter should change between Open and Closed.

⇒	If the parameter does not change between the commanded states, refer to Door Open Switch Malfunction - Front.

2. Observe the scan tool Passenger Door Open Sw. parameter while opening and closing the front passenger door. The parameter should change between Open and Closed.

⇒	If the parameter does not change between the commanded states, refer to Door Open Switch Malfunction - Front.

3. Observe the scan tool Ctsy. Lamp Actv. Reason parameter while opening and closing each rear door one at a time. The parameter should change between Door Open and Door Closed.

⇒	If the parameter does not change between the commanded states, refer to Door Open Switch Malfunction - Rear.

4. Ignition ON, all doors CLOSED, observe the scan tool Ctsy. Lamp Actv. Reason parameter while turning the dome lamp switch ON and OFF. The parameter should change between Off and Manual.

⇒	If the parameter does not change between the commanded states, refer to Dome Lamp Switch Malfunction.

5. If all scan tool parameters test normal, refer to the appropriate diagnostic procedure listed below.

•	Courtesy/Reading Lamps Malfunction - with Courtesy Lamp Module

•	Front Door Courtesy Lamp Malfunction

•	Courtesy Lamp Malfunction - w/o Courtesy Lamp Module

•	Inadvertent Power Courtesy Lamps Malfunction

•	Overhead Console Courtesy/Reading Lamp Malfunction - Limo/Hearse

•	Roof Rail Courtesy/Reading Lamp Malfunction - Limo/Hearse

Door Open Switch Malfunction - Front

1. Ignition OFF, disconnect the harness connector at the inoperative door latch assembly.
2. Ignition OFF and the appropriate door control module fuse removed, test for less than 5 ohms between the appropriate ground circuit terminal listed below and ground.

•	Driver Front Door Latch Assembly terminal 4

•	Passenger Front Door Latch Assembly terminal 1

⇒	If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the door control module

3. Ignition ON, verify the appropriate scan tool Door Open Sw. parameter is Inactive.

⇒	If not the specified value, test the appropriate signal circuit listed below for a short to ground. If the circuit tests normal, replace the appropriate door control module.

•	Driver front door latch assembly terminal 1

•	Passenger front door latch assembly terminal 4

4. Install a 3A fused jumper wire between the appropriate signal circuit terminal listed below and ground. Verify the related scan tool Door Open Sw. parameter is Open.

•	Driver front door latch assembly terminal 1

•	Passenger front door latch assembly terminal 4

⇒	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 door control module.

5. If all circuits test normal, test or replace the inoperative door latch assembly.

Door Open Switch Malfunction - Rear or Middle

1. Ignition OFF, disconnect the harness connector at the appropriate rear door lock assembly.
2. Test for less than 5 ohms between the appropriate ground circuit terminal listed below and ground.

•	Left rear door lock terminal 4

•	Left middle door lock terminal 4

•	Right rear door lock terminal 1

•	Right middle door lock terminal 1

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

3. Ignition ON, all doors closed, verify the scan tool Ctsy. Lamp Actv. Reason. parameter is Door Closed.

⇒	If not the specified value, test the appropriate signal circuit listed below for a short to ground. If the circuit tests normal, replace the BCM.

•	Left rear door lock terminal 1

•	Left middle door lock terminal 1

•	Right rear door lock terminal 4

•	Right middle door lock terminal 4

4. Install a 3A fused jumper wire between the appropriate signal circuit terminal listed below and ground. Verify the scan tool Ctsy. Lamp Actv. Reason parameter is Door Open.

•	Left rear door lock terminal 1

•	Left middle door lock terminal 1

•	Right rear door lock terminal 4

•	Right middle door lock terminal 4

⇒	If not the specified value, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the BCM.

5. If all circuits test normal, test or replace the door latch assembly.

Dome Lamp Switch Malfunction

1. Ignition OFF, disconnect the harness connector at the headlamp switch.
2. Verify that a test lamp illuminates between the ground circuit terminal 8 and B+.

⇒	If the test lamp does not illuminate, test the ground circuit for an open/high resistance.

3. Ignition ON, all doors closed, verify the scan tool Ctsy. Lamp Actv. Reason parameter is Off or Door Closed.

⇒	If not the specified value, test the signal circuit terminal 12 for a short to ground. If the circuit tests normal, replace the BCM.

4. Install a 3A fused jumper wire between the signal circuit terminal 12 and ground. Verify the scan tool Ctsy. Lamp Actv. Reason parameter is Manual.

⇒	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 BCM.

5. If all circuits test normal, test or replace the headlamp switch.

Courtesy/Reading Lamps Circuit Malfunction - with Courtesy Lamp Module

1. Ignition OFF, disconnect the X3 and X4 harness connectors at the BCM.
2. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminals listed below and ground.

•	B+ terminal 2 X3

•	B+ terminal 2 X4

⇒	If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test the related courtesy lamp supply voltage circuits for a short to ground.

3. Ignition OFF, connect the harness connectors at the BCM.
4. Disconnect the harness connector at the courtesy lamp module.
5. Ignition OFF, test for less than 5 ohms between the ground circuit terminal 7 and ground.

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

6. Ignition ON, verify that a test lamp illuminates between the control circuit terminal 8 and ground.

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

7. Door OPEN, verify that a test lamp illuminates between the control circuit terminal 6 and ground.

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

8. Disconnect the harness connector at the inoperative courtesy lamp.
9. Ignition OFF, test for less than 5 ohms between the ground circuit terminal B and ground.

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

10. Verify that a test lamp illuminates between the control circuit terminal A and ground.

⇒	If the test lamp does not illuminate, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the courtesy lamp module.

11. Door OPEN, verify that a test lamp illuminates between the control circuit terminal C and ground.

⇒	If the test lamp does not illuminate, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the courtesy lamp module.

12. If all circuits test normal, test or replace the courtesy lamp.

Front Door Courtesy Lamp Malfunction

1. Ignition OFF, disconnect the harness connector at the appropriate door courtesy lamp.
2. Ignition OFF and the appropriate door control module fuse removed, test for less than 5 ohms between the ground circuit terminal B and ground.

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

3. Connect a test lamp between the control circuit terminal A and the ground circuit terminal B.
4. Ignition ON, command the appropriate Door Switch Puddle/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 appropriate door control module.

⇒	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 appropriate door control module.

5. If all circuits test normal, test or replace the door courtesy lamp.

Courtesy Lamp Circuit Malfunction - w/o Courtesy Lamp Module

1. Ignition OFF, disconnect the harness connector at the inoperative courtesy lamp.
2. Ignition OFF, test for less than 5 ohms between the ground circuit terminal B and ground.

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

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

5. If all circuits test normal, test or replace the inoperative courtesy lamp.

Inadvertent Power Courtesy Lamps Malfunction

1. Ignition OFF, disconnect the X3 harness connector at the BCM.
2. Verify that a test lamp illuminates between the 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. If the circuit tests normal and the B+ circuit fuse is open, test the inadvertent power courtesy lamp control circuits for a short to ground.

3. Ignition OFF, connect the harness connector at the BCM.
4. Disconnect the harness connector at the inoperative lamp.
5. Test for less than 5 ohms between the ground circuit terminal B and ground.

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

6. Ignition ON, verify that a test lamp illuminates between the control circuit terminal A and ground.

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

7. If all circuits test normal, test or replace the inoperative lamp.

Overhead Console Courtesy/Reading Lamp Malfunction - Limo/Hearse

1. Ignition OFF, disconnect the X3, X4 harness connectors at the BCM.
2. Verify that a test lamp illuminates between the B+ circuit terminals listed below and ground.

•	B+ terminal 2 X3

•	B+ terminal 2 X4

⇒	If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test the related courtesy lamp supply voltage circuits for a short to ground.

3. Ignition OFF, connect the harness connectors at the BCM.
4. Disconnect the harness connector at the overhead console lamp.
5. Test for less than 5 ohms between the ground circuit terminal A and ground.

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

6. Verify that a test lamp illuminates between the control circuit terminal C and ground.

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

7. Remove the OVRHD LAMPS LIMO Relay from the rear fuse block.
8. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 1 and ground.

⇒	If the test lamp illuminates, test the control circuit for a short to voltage.

9. Ignition OFF, test for less than 5 ohms between the ground circuit terminal 3 and ground.

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

10. Verify that a test lamp illuminates between the control circuit terminal 5 and ground.

⇒	If the test lamp does not illuminate, test the control circuit for an open/high resistance.

11. Connect the harness connector at the overhead console lamp.
12. Connect a 3A fused jumper wire between the control circuit terminal 5 and the control circuit terminal 1. Verify the overhead lamp courtesy lamp is illuminated.

⇒	If the courtesy lamp does not illuminate, test the control circuit terminal 5 for a short to ground or an open/high resistance. If the circuit tests normal, test or replace the overhead courtesy lamp.

13. Connect a test lamp between the control circuit terminal 4 and ground.
14. 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 supply voltage circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.

15. If all circuits test normal, test or replace the overhead lamp relay.

Roof Rail Courtesy/Reading Lamp Malfunction - Limo/Hearse

1. Ignition OFF, disconnect the X3 and X4 harness connectors at the BCM.
2. Verify that a test lamp illuminates between the B+ circuit terminals listed below and ground.

•	B+ terminal 2 X3

•	B+ terminal 2 X4

⇒	If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test the related courtesy lamp supply voltage circuits for a short to ground.

3. Ignition OFF, connect the harness connectors at the BCM.
4. Disconnect the harness connector at the inoperative roof rail courtesy/reading lamp.
5. Test for less than 5 ohms between the ground circuit terminal B and ground.

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

6. Door open, verify that a test lamp illuminates between the control circuit terminal A and ground.

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

7. Verify that a test lamp illuminates between the control circuit terminal C and ground.

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

8. If all circuits test normal, test or replace the inoperative roof rail reading lamp.

Relay Test

1. Ignition OFF, disconnect the relay.
2. Test for 70-100 ohms 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.

Door Open Switch Test

1. Ignition OFF, remove the appropriate door lock actuator.
2. Test for infinite resistance between the appropriate signal and low reference terminals listed below with the switch in the open position.

•	Driver door -- signal terminal 1 and low reference terminal 4

•	Passenger door -- signal terminal 4 and low reference terminal 1

•	Left rear door -- signal terminal 1 and ground terminal 4

•	Right rear door -- signal terminal 4 and ground terminal 1

⇒	If not the specified value, replace the appropriate door lock actuator.

3. Test for less than 2 ohms between the appropriate signal and ground terminals listed below with the switch in the closed position.

•	Driver door -- signal terminal 1 and low reference terminal 4

•	Passenger door -- signal terminal 4 and lo reference terminal 1

•	Left rear door -- signal terminal 1 and ground terminal 4

•	Right rear door -- signal terminal 4 and ground terminal 1

⇒	If greater than the specified range, replace the appropriate door lock actuator.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.