Power Liftgate System Description

WARNING: This page is about a different car, the 2013 GMC Acadia, 2013 Chevrolet Traverse, and 2013 Buick Enclave. However, it is still accessible from the selected car via links, so may be relevant.

Liftgate Module

The liftgate module controls the liftgate motor, liftgate clutch, and liftgate latch based on various inputs. The liftgate module also performs diagnostics on these inputs and outputs and will disable liftgate functionality and set DTCs should a fault be detected. The liftgate module is secured to the motor assembly at the left rear of the vehicle. The module requires a liftgate position learn procedure be performed when replacing. This allows the module to learn the full open and full closed positions of the liftgate.

Liftgate Motor Assembly

The motor assembly is located at the left rear of the vehicle and contains the liftgate motor, liftgate clutch, hall effect sensor, and the open switch. The motor assembly also provides means to open the liftgate by way of a gear set. During operation, the liftgate motor drives the gear set that raises and lowers the liftgate through a strut rod connected to a lever which is part of the gear set. The liftgate module applies voltage and provides ground to operate the liftgate motor and clutch. When liftgate operation is requested, the liftgate module engages the clutch and begins driving the motor. If a fault were to occur that requires the disabling of liftgate functions, the liftgate module would release the clutch, allowing manual operation of the liftgate. The liftgate module determines the position of the liftgate based on the hall effect sensor and open switch. The liftgate module applies voltage and provides a ground path to power the hall effect switch. As the liftgate is in motion, the hall effect switch rotates, alternately pulsing the applied voltage on each of the 2 hall effect signal circuits. The liftgate module determines the position based on the number of hall pulses, or counts, received. When the liftgate is fully open, the open switch is closed. This provides an input to the liftgate to indicate the liftgate has reached its full open position.

Liftgate Latch

The liftgate latch contains the cinch/release motor, as well as 3 liftgate switches. Each of the 3 switches contained within provide a discrete input to the liftgate module. These switches act as a liftgate open switch, a liftgate ajar switch, and a cinch/release switch. The liftgate module looks at these inputs to determine when the liftgate has cleared the latch during opening and to determine when the liftgate is seated in the latch during closing. When the liftgate open and ajar switches are seen to be closed, indicating a closed liftgate, the liftgate module will command the cinch/release motor to cinch, pulling the liftgate tightly closed. When a liftgate open operation is requested, the cinch/release motor will release, allowing the liftgate to clear the latch and begin opening.

Right/Left Side Upper Sensor

On each side of the liftgate opening is an object detection sensor. These 2 sensors will disable liftgate closing or reverse an already in motion liftgate should an object be seen in the path of the liftgate. The sensors are pressure sensitive sealing strips located on the upper C-pillar of the vehicle. If pressure is applied to either strip, an input will be sent to the liftgate module signifying that an object has been detected.

Liftgate Handle Switch

Located in the liftgate handle is the liftgate handle switch. This switch provides a discrete input to the liftgate to indicate when a liftgate release operation is requested. Opening the liftgate using the handle will not cause the liftgate to automatically raise. Only the liftgate latch is released when using the handle.

Liftgate Close Switch

Accessible only when the liftgate is open, the liftgate closed switch provides a discrete input to the liftgate module to indicate when a liftgate close operation is requested.

Liftgate Ajar Indicator

The driver information center (DIC) located on the instrument panel cluster (IPC), illuminates the LIFT GATE AJAR indicator when the power lift gate module (PLM) detects the liftgate latch ajar switch is closed to ground indicating the liftgate is open. The IPC receives a GMLAN serial data message from the PLM indicating the liftgate ajar status. If this message is displayed and the vehicle speed is greater than 4.8 km/h (3 mph), a chime will sound.