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
--- | --- | --- | --- | ---
Door Ajar Switch Voltage Supply Circuit | 1 | 2 | -- | --
Dome Lamp Switch | 1 | 2 | -- | --
BCM | 1 | 2 | 2 | --
Door Ajar Switch | 1 | 2 | 2 | --
1. Courtesy Lamps Always ON 2. Courtesy Lamps Inoperative

### Circuit/System Description

The courtesy lamps are controlled by the body control module (BCM). Inputs from the dome lamp switch and the door ajar switches are monitored by the BCM. When a door ajar switch is closed the BCM supplies the ground for the courtesy lamps or the dome lamp switch is turned to the ON position. The BCM also supplies the voltage for the courtesy lamps.

### Diagnostic Aids

• | Check for the proper operation of the courtesy lamp bulbs.

• | Check the position of the dome lamp switch.

### Reference Information

#### Schematic Reference

Interior Lights Schematics

#### Connector End View Reference

Lighting Systems Connector End Views

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

• | Scan Tool Data Definitions

• | Scan Tool Data List

• | Scan Tool Output Controls

### Circuit/System Verification

Ignition ON, observe the Scan Tool Door Lamp Command parameter while OPENING and CLOSING the drive door. The reading should change between OFF and ON.

### Circuit/System Testing

#### Dome Lamp Switch Circuit Testing

1. Ignition OFF, disconnect the harness connector at the dome lamp switch.
2. Ignition OFF, test for less than 1 ohm of resistance between the ground circuit and ground.

⇒ | If greater than 1 ohm, test the ground circuit for an open/high resistance.

3. Verify the scan tool dome lamp command parameter is OFF.

⇒ | If the dome lamp command is not OFF, test the signal circuit for a short to ground. If the circuit tests normal, replace the BCM.

4. If all circuits test normal, test or replace the dome lamp switch.

#### Door Ajar Switch Circuit Testing

Important: This test can be performed on any of the door ajar switches.

1. Ignition OFF, disconnect the harness connector at the inoperative door ajar switch.
2. Ignition OFF, test for less than 1 ohm of resistance between the ground circuit and ground.

⇒ | If greater than 1 ohm, test the ground circuit for an open/high resistance.

3. Verify the scan tool dome lamp command parameter is OFF.

⇒ | If the dome lamp command is not OFF, test the signal circuit for a short to ground. If the circuit tests normal, replace the BCM.

4. If all circuits test normal, test or replace the door ajar switch.

### Component Testing

#### Dome Lamp Switch Testing

1. Ignition OFF, disconnect the harness connector at the dome lamp switch.
2. Test for infinite resistance between the three signal terminals with the switch being in the opposite position and the voltage supply terminal.

⇒ | If less than infinite resistance, replace the dome lamp switch.

3. Test for less than 2 ohms between each of the signal terminals with the switch in the appropriate position and the voltage supply terminal.

⇒ | If greater than 2.1 ohms, replace the dome lamp switch.

#### Door Ajar Switch Testing

Important: This test can be preformed on any of the door ajar switches.

1. Ignition OFF, disconnect the harness connector at the door ajar switch.
2. Test for infinite resistance between the signal terminal and the voltage supply terminal with the switch in the open position.

⇒ | If less than infinite resistance, replace the door ajar switch.

3. Test for less than 1 ohms between the signal terminal and the voltage supply terminal with the switch in the closed position.

⇒ | If greater than 1 ohms, replace the door ajar switch.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Dome Lamp Replacement

• | Front Side Door Latch Replacement

• | Rear Side Door Latch Replacement

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