• 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.

For symptom byte information refer to: Symptom Byte List

The liftgate motor is a bi-directional motor and open or close operation is the result of the direction of the motor rotation. The liftgate control module controls the liftgate motor through the control circuits by supplying power and ground in the appropriate polarity. The motor control circuits are monitored by the liftgate control module prior to activation for a high or low condition and during motor operation for any irregular current flow conditions.

• The system voltage is 9–16 V.
• Power open or close function is initiated.

The liftgate control module detects a short to battery in the liftgate motor control circuits.

The liftgate control module detects a short to ground in the liftgate motor control circuits.

The liftgate control module detects an open/high resistance in the liftgate motor control circuits or an open/high resistance in the terminal 3 X2 B+ circuit

The liftgate will release but will not power open or power close

• The DTC will be current for as long as the fault is present.
• When the fault is no longer present, the DTC will be a history DTC.
• A history DTC will clear after 50 ignition cycles.

Whenever the liftgate control module loses power or is disconnected, the ignition must be cycled OFF then ON in order to reactivate the liftgate control module.

In some circumstances high or low control circuit faults may cause the liftgate control module to react as if the liftgate has encountered an object in its travel and reverse direction.

Liftgate Schematics

Master Electrical Component List

Liftgate Description and Operation

• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs

Control Module References for scan tool information

1. Ignition ON.
2. Verify the liftgate will OPEN and CLOSE when commanding the Liftgate Open/Close with a scan tool.
• If the liftgate does not OPEN or CLOSE

  Refer to Circuit/System Testing

• If the liftgate does OPEN and CLOSE
3. All OK.

1. Ignition OFF, disconnect the X2 harness connector at the K39 Liftgate Control Module, 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 Ω in the B+ circuit end to end.
• If 2 Ω or greater, repair the open/high resistance in the circuit.
• If less than 2 Ω, 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 M17 Liftgate Motor Assembly.
4. Test for infinite resistance between each control circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance, replace the M17 Liftgate Motor Assembly.
• If the test lamp illuminates
3. Ignition OFF, connect the X2 harness connector at the K39 Liftgate Control Module and disconnect the harness connector at the M17 Liftgate Motor Assembly.
4. Connect a test lamp between the control circuit terminal 1 and control circuit terminal 5, ignition ON.

Note: The liftgate must be opened and allowed to cinch closed each time this test is performed, repeating this test without opening and closing the liftgate will result in a misdiagnosis and replacement of a functional K39 Liftgate Control Module

5. Open and completely close the liftgate, verify the test lamp turns ON and OFF when pressing the S46B Liftgate Unlatch Switch.
• If the test lamp remains OFF
1. Ignition OFF, remove the test lamp, disconnect the X3 harness connector at the K39 Liftgate Control Module.
2. Test for infinite resistance between each 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 Ω in the control circuits end to end.
• If 2 Ω or greater, repair the open/high resistance in the circuit.
• If less than 2 Ω, replace the K39 Liftgate Control Module.
• If the test lamp is always ON
1. Ignition OFF, remove the test lamp, disconnect the X3 harness connector at the K39 Liftgate Control Module, ignition ON.
2. Test for less than 1 V between each control circuit and ground.
• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V, replace the K39 Liftgate Control Module
• If the test lamp turns ON and Off
6. Replace the M17 Liftgate Motor Assembly.

Perform the Diagnostic Repair Verification after completing the repair.

• Liftgate Power Assist Actuator Replacement
• Control Module References for the liftgate control module replacement, programming and setup