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.

### Circuit/System Description

The body control module (BCM) receives a discrete input from the rear compartment lid ajar switch signal circuit. When the rear compartment lid release actuator releases the rear compartment lid, the rear compartment lid ajar switch, which is internal to the rear compartment lid release actuator, is supplied with ground which causes the trunk ajar switch signal circuit to be pulled low. The BCM interprets this and communicates via serial data with the instrument panel cluster. When the trunk is open/ajar and the vehicle is in any gear other than Park, the driver information center will display TRUNK OPEN. If the trunk is still open and the vehicle speed is greater than 5 km/h (3 MPH) a chime will sound.

### Reference Information

#### Schematic Reference

Release Systems Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

Luggage Compartment 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

Ignition ON, observe the scan tool Rear Closure Ajar Switch parameter while opening and closing the trunk. The parameter should change between Inactive and Active.

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the M40 Rear Compartment Lid Latch.
2. Ignition ON, verify the scan tool Rear Closure Ajar Switch parameter is Inactive.

⇒ | If not the specified value, test the signal circuit terminal 4 for a short to ground. If the circuit tests normal, replace the K9 Body Control Module (BCM).

3. Install a 3 A fused jumper wire between the signal circuit terminal 4 and ground. Verify the scan tool Rear Closure Ajar Switch parameter is Active.

⇒ | If not the specified value, test the signal circuit terminal 4 for a short to voltage or and open/high resistance. If the circuit tests normal, replace the K9 Body Control Module (BCM).

4. If all circuits test normal, test or replace the M40 Rear Compartment Lid Latch.

### Component Testing

1. Ignition OFF, disconnect the harness connector at the M40 Rear Compartment Lid Latch.
2. Test for infinite resistance between the signal terminal 4 and the ground terminal 2 with the switch in the open position.

⇒ | If not the specified value, replace the M40 Rear Compartment Lid Latch.

3. Test for less than 2 Ω between the signal terminal 4 and the ground terminal 2 with the switch in the closed position.

⇒ | If greater than the specified range, replace the M40 Rear Compartment Lid Latch.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Rear Compartment Lid Latch Replacement

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