Chevrolet Trax: Liftgate release malfunction

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/System Description

The liftgate unlatch switch is an input to the body control module (BCM). The BCM supplies a 12 V signal to the liftgate unlatch switch and when the switch is pressed, signal circuit voltage goes low. When the BCM receives a liftgate 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 liftgate release relay coil, energizing the relay. When the relay is energized, battery voltage flows through the closed contacts of the relay to the liftgate latch assembly which activates allowing for the liftgate to be raised to the open position.

Diagnostic Aids

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

Reference Information

Schematic Reference

Release Systems Schematics (Encore), Release Systems Schematics (Trax)

Connector End View Reference

WIRING SYSTEMS AND POWER MANAGEMENT - COMPONENT CONNECTOR END VIEWS - INDEX - ENCORE WIRING SYSTEMS AND POWER MANAGEMENT - COMPONENT CONNECTOR END VIEWS - INDEX - TRAX

Description and Operation

Rear Hatch/Gate 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.
2. Verify the scan tool Trunk Lid/Liftgate Window Exterior Unlatch Switch parameter changes between Inactive and Active when pressing the S46B Liftgate Unlatch Switch.

• If the parameter does not change

Refer to Circuit/System Testing - Liftgate Release Switch Inoperative.

• If the parameter changes

NOTE:

Verify all doors have been commanded UNLOCK with a scan tool prior to commanding the liftgate to unlatch

3. Verify the M30 Liftgate Latch functions when commanding the Liftgate Unlatch with a scan tool.

• If the M30 Liftgate Latch does not UNLATCH

Refer to Circuit/System Testing - Liftgate Latch Inoperative

• If the M30 Liftgate Latch does UNLATCH

4. All OK.

Circuit/System Testing

Liftgate Release Switch Inoperative

1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the S46B Liftgate Unlatch Switch. 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, remove the jumper wire, 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 S46B Liftgate Unlatch Switch.

Liftgate Latch Inoperative

1. Ignition OFF, disconnect the KR95A Liftgate Unlatch Relay. Ignition ON.
2. 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 M30 Liftgate 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 KR95A Liftgate Unlatch Relay
• If the test lamp illuminates

3. Connect a test lamp between the control circuit terminal 2 and ground.
4. Ignition ON, verify the test lamp turns ON and OFF when commanding the Liftgate Unlatch with a scan tool.

• If the test lamp is always OFF

1. Ignition OFF, remove the test lamp, 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, remove the test lamp, 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

5. Connect a test lamp between the control circuit terminal 1 and B+.
6. Verify the test lamp turns ON and OFF when commanding the Liftgate Unlatch with a scan tool.

• If the test lamp is always OFF

1. Ignition OFF, remove the test lamp, 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

3. Ignition OFF.
4. 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, remove the test lamp, 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, 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 M30 Liftgate 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 1 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 M30 Liftgate 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 M30 Liftgate Latch is activated.

• If the M30 Liftgate Latch does not activate

1. Ignition OFF, disconnect the harness connector at the M30 Liftgate 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, test or replace the M30 Liftgate Latch.
• If the M30 Liftgate Latch activates

13. Test or replace the KR95A Liftgate Unlatch Relay.

Component Testing

Liftgate Latch

1. Ignition OFF, disconnect the harness connector at the M30 Liftgate Latch.
2. Install a 10 A fused jumper wire between the control terminal 3 and 12 V. Install a jumper wire between the ground terminal 1 and ground.
3. Verify the M30 Liftgate Latch activates

• If the M30 Liftgate Latch does not activate

Replace the M30 Liftgate Latch.

• If the M30 Liftgate Latch does activate.

4. All OK

Liftgate Release Switch

1. Ignition OFF, disconnect the harness connector at the S46B Liftgate Unlatch Switch.
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 S46B Liftgate Unlatch Switch.

• 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 S46B Liftgate Unlatch Switch.

• If less than 3 ohms

4. All OK

Relay Test

1. Ignition OFF, disconnect the KR95A Liftgate Unlatch Relay.
2. Test for 60-200 ohms between terminals 85 and 86.

• If less than 60 or greater than 200

Replace the KR95A Liftgate Unlatch Relay.

• If between 60-200 ohms

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

• 30 and 86
• 30 and 87
• 30 and 85
• 85 and 87
• If less than infinite resistance

Replace the KR95A Liftgate Unlatch Relay.

• If infinite resistance

4. Install a 3 A fused jumper wire between relay terminal 85 and 12 V. Install a jumper wire between relay terminal 86 and ground.
5. Test for less than 2 ohms between terminals 30 and 87.

• If 2 ohms or greater

Replace the KR95A Liftgate Unlatch Relay.

• If less than 2 ohms

6. All OK

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• Relay Replacement (Within an Electrical Center) , Relay Replacement (Attached to Wire Harness)
• Liftgate Release Switch Replacement
• Liftgate Latch Replacement
• Control Module References for BCM replacement, programming and setup

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