Principles of Operation

PRINCIPLES OF OPERATION

The power liftgate feature allows the customer to automatically OPEN or CLOSE the liftgate by activating the interior open/close switch, the remote keyless entry transmitter or by manually initiating movement. The power liftgate uses a power cinching system to latch the liftgate.

The power liftgate system consists of the:
- power liftgate control switch (located in the overhead console).
- power liftgate motors (located in the rear headliner area).
- optical sensor and encoder wheel (located on the left power liftgate motor assembly).
- pinch strip switches (located on the body above the taillamps).
- cinching latch (located in the middle lower portion of the liftgate).
- forkbolt switch (located in the cinching latch mechanism).
- detent switch (located in the cinching latch mechanism).
- liftgate latch remote control (located in the lower right-hand area of the liftgate).
- home position switch (located on the liftgate latch remote control).
- liftgate latch lock/unlock actuator (located in the lower left-hand area of the liftgate).
- power liftgate module (located behind the left rear quarter trim panel).

The power liftgate is controlled by the power liftgate module.

The power liftgate module receives inputs from:
- glass position switch (determines the ajar status of the liftgate glass).
- forkbolt switch (determines the primary position of the latch).
- detent switch (determines the secondary position of the latch).
- home switch (determines the power cinch status).
- power liftgate control switch (activates the power liftgate from the interior of vehicle).
- pinch strip switches (determines if an obstacle is between the pinch strip and liftgate).
- instrument cluster module (activates and sets the options for the power liftgate).
- optical sensor and encoder wheel (determines the direction, travel speed and obstacle detection of the liftgate).
- UBP serial communication link.
- power deployable running boards (if equipped).

The power liftgate module sends outputs to:
- liftgate motors.
- power cinching latch system.
- liftgate close chime module.
- body security module.
- power deployable running boards (if equipped).

The liftgate close chime module provides the sounding of an audible chime (housed in a unit external from the power liftgate module) whenever a powered closing operation is initiated. The chime sound serves as a warning to alert the vehicle occupants and any bystanders that the liftgate is being moved in a closing direction by a powered operation. The power liftgate module controller will activate the external chime unit's continuous chime mode through a discrete high side drive output signal. The output will be asserted for a period of 4 seconds, resulting in the chime sounding for a period of 4 seconds. The gate will not be moved for the first second, as a pre-warning of impending gate movement. During that initial first second, the power liftgate module may energize the gate drive system at a low power level that is intended to cause little (3 degrees maximum) to no gate movement. This is done to take up drive unit slack in advance, so that gate closure times meet the open/close cycle time requirement.

The power liftgate may not operate under the following conditions:
- A low voltage or dead battery
- A disconnected battery
- A power liftgate that has been left open for more than 6 hours
- A power liftgate that has been manually closed and left ajar

If any of these conditions has occurred, the power liftgate must be reset before performing any pinpoint tests. Refer to Power Liftgate Initialization.