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Trunk Release Malfunction




Trunk Release Malfunction

Diagnostic Instructions

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

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

* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.

Diagnostic Fault Information






Circuit/System Description

The rear compartment lid unlatch switch is an input to the Body Control Module (BCM). The BCM supplies a 12 V signal to the rear compartment lid unlatch switch and when the switch is pressed, signal circuit voltage goes low. When the BCM receives a trunk release signal it will monitor the status to the door latches. If the vehicle doors are locked, the BCM will ignore the request, if the doors are unlocked, the BCM will supply voltage and ground to the rear compartment lid release relay coil, energizing the relay. When the relay is energized, battery voltage flows through the closed contacts of the relay to the rear compartment lid latch which activates allowing for the trunk lid to be raised to the open position.

Diagnostic Aids

An intermittent short to ground in the rear compartment lid unlatch switch circuit may cause the BCM to command the trunk to open if the vehicle is in park and the doors are unlocked. If the vehicle has a history of the trunk opening unexpectedly, inspect the point where the wires enter the rear compartment lid unlatch switch for corrosion or evidence of water intrusion.

Reference Information

Schematic Reference

Release Systems Schematics Release Systems Schematics

Connector End View Reference

Component Connector End Views Fuel Pump and Level Sensor Assembly

Description and Operation

Luggage Compartment Description and Operation Description and Operation

Electrical Information Reference

* Circuit Testing Circuit Testing

* Connector Repairs Connector Repairs

* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections

* Wiring Repairs Wiring Repairs

Scan Tool Reference

Control Module References Control Module References for scan tool information

Circuit/System Verification

1. Ignition ON.

2. Verify the scan tool Trunk Lid/Liftgate Window Exterior Unlatch Switch parameter changes between Active and Inactive when pressing and releasing the S58A Rear Compartment Lid Unlatch Switch-Exterior.

• If the parameter does not change
Refer to Circuit/System Testing - Trunk Release Switch Inoperative

• If the parameter changes

3. Verify the operation of the M40 Rear Compartment Lid Latch when commanding the Trunk Lid Unlatch with a scan tool.

• If the M40 Rear Compartment Lid Latch does not UNLATCH
Refer to Circuit/System Testing - Release Actuator Inoperative

• If the M40 Rear Compartment Lid Latch does UNLATCH

4. All OK.

Circuit/System Testing

Trunk Release Switch Inoperative

1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the S58A Rear Compartment Lid Unlatch Switch-Exterior. It may take up to 2 minutes for all vehicle systems to power down.

2. Test for less than 10 ohms between the ground circuit terminal 2 and ground.

• If 10 ohms or greater

1. Ignition OFF.

2. Test for less than 2 ohms in the ground circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms, repair the open/high resistance in the ground connection.

• If less than 10 ohms

3. Ignition ON.

4. Verify the scan tool Trunk Lid/Liftgate Window Exterior Unlatch Switch parameter is Inactive.

• If not Inactive

1. Ignition OFF, disconnect the harness connector at the K9 Body Control Module.

2. Test for infinite resistance between the signal circuit terminal 1 and ground.

• If less than infinite resistance, repair the short to ground on the circuit.

• If infinite resistance, replace the K9 Body Control Module.

• If Inactive

5. Install a 3 A fused jumper wire between the signal circuit terminal 1 and the ground circuit terminal 2.

6. Verify the scan tool Trunk Lid/Liftgate Window Exterior Unlatch Switch parameter is Active.

• If not Active

1. Ignition OFF, disconnect the harness connector at the K9 Body Control Module, ignition ON.

2. Test for less than 1 V between the signal circuit and ground.

• If 1 V or greater, repair the short to voltage on the circuit.

• If less than 1 V

3. Test for less than 2 ohms in the signal circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms, replace the K9 Body Control Module.

• If Active

7. Test or replace the S58A Rear Compartment Lid Unlatch Switch-Exterior.

Release Actuator Inoperative

1. Ignition OFF and all vehicle systems OFF, disconnect the KR95B Rear Compartment Lid Unlatch Relay. It may take up to 2 minutes for all vehicle systems to power down.

2. Test for less than 10 ohms between the ground circuit terminal 2 and ground.

• If 10 ohms or greater

1. Ignition OFF.

2. Test for less than 2 ohms in the ground circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms, repair the open/high resistance in the ground connection.

• If less than 10 ohms

3. Ignition ON.

4. Verify a test lamp illuminates between the B+ circuit terminal 3 and ground.

• If the test lamp does not illuminate and the circuit fuse is good

1. Ignition OFF.

2. Test for less than 2 ohms in the B+ circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms, verify the fuse is not open and there is voltage at the fuse.

• If the test lamp does not illuminate and the circuit fuse is open

1. Ignition OFF.

2. Test for infinite resistance between the B+ circuit and ground.

• If less than infinite resistance, repair the short to ground on the circuit.

• If infinite resistance,

3. Disconnect the harness connector at the M40 Rear Compartment Lid Latch.

4. Test for infinite resistance between the control circuit terminal 5 and ground.

• If less than infinite resistance, repair the short to ground on the circuit.

• If infinite resistance, replace the KR95B Rear Compartment Lid Unlatch Relay

• If the test lamp illuminates

5. Connect a test lamp between the control circuit terminal 1 and the ground circuit terminal 2.

6. Verify the test lamp briefly turns ON when commanding the Trunk Lid Unlatch with a scan tool.

• If the test lamp is always OFF

1. Ignition OFF, disconnect the harness connector at the K9 Body Control Module.

2. Test for infinite resistance between the control circuit and ground.

• If less than infinite resistance, repair the short to ground on the circuit.

• If infinite resistance

3. Test for less than 2 ohms in the control circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms, replace the K9 Body Control Module.

• If the test lamp is always ON

1. Ignition OFF, disconnect the harness connector at the K9 Body Control Module, ignition ON.

2. Test for less than 1 V between the control circuit and ground.

• If 1 V or greater, repair the short to voltage on the circuit.

• If less than 1 V, replace the K9 Body Control Module.

• If the test lamp turns ON and OFF

7. Verify that a test lamp does not illuminate between the control circuit terminal 5 and ground.

• If the test lamp illuminates
Repair the short to voltage on the control circuit

• If the test lamp does not illuminate

8. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the M40 Rear Compartment Lid Latch. It may take up to 2 minutes for all vehicle systems to power down.

9. Test for less than 10 ohms between the ground circuit terminal 2 and ground.

• If 10 ohms or greater

1. Ignition OFF.

2. Test for less than 2 ohms in the ground circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms, repair the open/high resistance in the ground connection.

• If less than 10 ohms

10. Connect the harness connector at the M40 Rear Compartment Lid Latch

11. Ignition ON, connect a 10 A fused jumper wire between the B+ circuit terminal 3 and the control circuit terminal 5.

12. Verify the M40 Rear Compartment Lid Latch is activated.

• If the M40 Rear Compartment Lid Latch does not activate

1. Ignition OFF, disconnect the harness connector at the M40 Rear Compartment Lid Latch.

2. Test for less than 2 ohms in the control circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms, replace the M40 Rear Compartment Lid Latch.

• If the M40 Rear Compartment Lid Latch activates

13. Test or replace the KR95B Rear Compartment Lid Unlatch Relay.

Component Testing

Rear Compartment Lid Latch

1. Ignition OFF, disconnect the harness connector at the M40 Rear Compartment Lid Latch.

2. Install a 10 A fused jumper wire between the control terminal 1 and 12 V. Install a jumper wire between the ground terminal 2 and ground.

3. Verify the M40 Rear Compartment Lid Latch activates

• If the M40 Rear Compartment Lid Latch does not activate.
Replace the M40 Rear Compartment Lid Latch.

• If the M40 Rear Compartment Lid Latch does activate.

4. All OK

Trunk Release Switch

1. Ignition OFF, disconnect the harness connector at the S58A Rear Compartment Lid Unlatch Switch-Exterior.

2. Test for infinite resistance between the signal terminal 1 and the ground terminal 2 with the switch in the open position.

• If less than infinite resistance
Replace the S58A Rear Compartment Lid Unlatch Switch-Exterior.

• If infinite resistance

3. Test for less than 3 ohms between the signal terminal 1 and the ground terminal 2 with the switch in the closed position.

• If 3 ohms or greater
Replace the S58A Rear Compartment Lid Unlatch Switch-Exterior.

• If less than 3 ohms

4. All OK

Relay Test

1. Ignition OFF, disconnect the KR95B Rear Compartment Lid Unlatch Relay.

2. Test for 60-200 ohms between terminals 1 and 3.

• If less than 60 ohms or greater than 200 ohms
Replace the KR95B Rear Compartment Lid Unlatch Relay.

• If between 60-200 ohms

3. Test for infinite resistance between the terminals listed below:

* 4 and 3

* 4 and 5

* 4 and 1

* 5 and 1

• If less than infinite resistance
Replace the KR95B Rear Compartment Lid Unlatch Relay.

• If infinite resistance

4. Install a 3 A fused jumper wire between relay terminal 3 and 12 V. Install a jumper wire between relay terminal 1 and ground.

5. Test for less than 2 ohms between terminals 4 and 5.

• If 2 ohms or greater
Replace the KR95B Rear Compartment Lid Unlatch Relay.

• If less than 2 ohms

6. All OK

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests after completing the repair.

* Relay Replacement (Within an Electrical Center) Relay Replacement (Within an Electrical Center)Relay Replacement (Attached to Wire Harness) Relay Replacement (Attached to Wire Harness)

* Rear Compartment Lid Latch Replacement Rear Compartment Lid Latch Replacement

* Liftgate Release Switch Replacement Service and Repair

* Control Module References Control Module References for BCM replacement, programming and setup

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