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 Lamp Control | 1 | B2555 05 | B2555 05 | --
Inside Rearview Mirror Lamps Control | B1480 00 | 1 | -- | --
Inadvertent Relay Control | B1480 00 | 1 | -- | --
Inside Rearview Mirror Ground | -- | 1 | -- | --
1. Courtesy Lamps Malfunction

### Circuit/System Description

The INT LIGHT fuse supplies battery voltage to the inadvertent load control relay located in the body control module (BCM). The BCM applies ground to the inadvertent relay control circuit which energizes the inadvertent load control relay coil. With the relay coil energized, the switch contacts close allowing battery voltage to flow from the INT LIGHT fuse to the inside rearview mirror lamps through the inside rearview mirror lamps supply voltage circuit. The inside rearview mirror lamps are controlled by a 3 position (OFF, DOOR, ON) switch. When the inside rearview mirror switch is placed in the DOOR position, the lamps are controlled by the BCM by grounding the courtesy lamp control circuit. When any door is opened, the jam switch contacts close and the BCM receives a door-open input. If the BCM receives a door lock or unlock input, the BCM will activate the inadvertent relay control circuit, providing battery voltage to the inside rearview mirror lamps. The BCM also provides ground to the inside rearview mirror lamps through the courtesy lamp control circuit.

### 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 Testing

1. Ignition OFF, disconnect the harness connector at the inside rearview mirror.
2. Ignition OFF, scan tool OFF, interior lamps OFF, test for less than 1 ohm between the appropriate ground circuit terminal listed below and ground.

• | Inside rearview mirror ground terminal 6

• | Inside rearview mirror ground terminal 8 - with UE1

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

3. Ignition OFF, scan tool OFF, interior lamps OFF, test for less than 1 ohm between the appropriate control circuit terminal listed below and ground.

• | Courtesy lamp control terminal 6

• | Courtesy lamp control terminal 1 - with UE1

⇒ | If greater than the specified range, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.

4. Ignition ON, verify that a test lamp illuminates between the appropriate control circuit terminal listed below and ground.

• | Inside rearview mirror lamps control terminal 7

• | Inside rearview mirror lamps control terminal 6 - with UE1

⇒ | 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.

5. If all circuits test normal, replace the inside rearview mirror.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Inside Rearview Mirror Replacement

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