For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• | Diagnostic Procedure Instructions provides an overview of each diagnostic category.

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Courtesy Lamps Control | 1 | 1 | -- | --
Courtesy Lamps Low Control | 1 | B2555 05 | B2555 05 | --
Park Lamp Control | 2 | 2 | 2 | --
Rear Compartment Courtesy Lamp Control | -- | 3 | 3 | --
Inside Rearview Mirror Ground | -- | 1 | -- | --
1. Courtesy Lamps Malfunction 2. Park, License, and/or Tail Lamps Malfunction 3. Rear Compartment Lamp Malfunction

### Circuit/System Description

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.

### Reference Information

#### 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

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

Control Module References for scan tool information

### Circuit/System Verification

1. Ignition ON, command the Interior Lamps ON and OFF with a scan tool. The courtesy lamps should turn ON and OFF when changing between the commanded states.

⇒ | If the courtesy lamps do not illuminate when commanded, refer to Illuminated Entry Lamps Malfunction.

2. Observe the scan tool Driver Door Ajar Sw. parameter while opening and closing the driver door. The parameter should change between Door Closed and Door Ajar.

⇒ | If the parameter does not change as the driver door is opened and closed, refer to Door Ajar Indicator Malfunction.

3. Observe the scan tool Door Ajar Switch parameter while opening and closing the front passenger and each rear door one at a time. The parameter should change between Door Closed and Door Ajar.

⇒ | If the parameter does not change as each door is opened and closed , refer to Door Ajar Indicator Malfunction.

4. Observe the scan tool Trunk Ajar Switch parameter while opening and closing the trunk. The parameter should change between Trunk Closed and Trunk Ajar.

⇒ | If the reading does not change as the trunk is opened and closed, refer to Trunk Ajar Indicator Malfunction.

5. Turn the individual reading lamps ON and OFF with there respective switches. The lamps should turn ON and OFF when activated.

⇒ | If the reading lamps do not turn ON and OFF, refer to Reading Lamps Malfunction.

### Circuit/System Testing

#### Illuminated Entry Lamps Malfunction

1. Ignition OFF, disconnect the harness connector at the inoperative dome lamp/inside rearview mirror assembly.
2. Ignition OFF, scan tool OFF, doors CLOSED, interior lamps OFF, test for less than 5 ohms between the appropriate ground circuit listed below and ground.

• | Dome lamp ground terminal A

• | Inside rearview mirror ground terminal 8 - with UE1

• | Inside rearview mirror low control terminal 2 - without UE1

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

3. Connect a test lamp between the appropriate control circuit terminal listed below and ground.

• | Dome lamp control terminal D

• | Inside rearview mirror control terminal 6 - with UE1

• | Inside rearview mirror control terminal 7 - without UE1

4. 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 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.

5. Connect a test lamp between B+ and the appropriate control circuit terminal listed below.

• | Dome lamp low control terminal B

• | Inside rearview mirror low control terminal 1 - with UE1

• | Inside rearview mirror low control terminal 6 - without UE1

6. Command the Inadvertent Power 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.

7. If all circuits test normal, replace the inoperative dome lamp or inside rearview mirror assembly.

#### Reading Lamps Malfunction

1. Ignition OFF, disconnect the harness connector at the inoperative dome lamp/inside rearview mirror assembly.
2. Ignition OFF, scan tool OFF, doors CLOSED, interior lamps OFF, test for less than 5 ohms between the appropriate ground circuit listed below and ground.

• | Dome lamp ground terminal A

• | Inside rearview mirror ground terminal 8 - with UE1

• | Inside rearview mirror low control terminal 2 - without UE1

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

3. Connect a test lamp between the appropriate control circuit terminal listed below and ground.

• | Dome lamp control terminal D

• | Inside rearview mirror control terminal 6 - with UE1

• | Inside rearview mirror control terminal 7 - without UE1

4. 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 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.

5. If all circuits test normal, replace the inoperative dome lamp or inside rearview mirror assembly.

#### Rear Compartment Lamp Malfunction

1. Ignition OFF, disconnect the harness connector at the rear compartment lamp.
2. Ignition OFF, trunk OPEN, verify that a test lamp illuminates between B+ and the control circuit terminal A.

⇒ | If the test lamp does not illuminate, test the control circuit for a short to voltage or an open/high resistance.

3. Ignition OFF, trunk OPEN, verify that a test lamp illuminates between the control circuit terminal B 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.

4. If all circuits test normal, replace the rear compartment courtesy lamp.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Cargo Lamp Replacement

• | Dome Lamp Replacement

• | Inside Rearview Mirror Replacement

• | Reading Lamp Replacement

• | Control Module References for BCM replacement, setup, and programming