Principles of Operation

PRINCIPLES OF OPERATION

Power and Ground Requirements
The smart junction box (SJB) fuse 14 (10A) supplies battery logic power required for the software, clutch and internal switching operations. Power is supplied to the motor by bussed electric center (BEC) fuse 27 (30A).

Ground for the power liftgate (PLG) module is a separate single connection. Some of the continuous inputs which are at a ground state when on are also used for logic switching.

Power Liftgate (PLG) Detent Switch, Forkbolt Primary Switch and Forkbolt Secondary Switch
The PLG detent switch, forkbolt primary switch and forkbolt secondary switch provide inputs to the PLG module in order to determine liftgate latch position. The PLG module receives inputs from the PLG detent switch, forkbolt primary switch and forkbolt secondary switch in the following manner:

Latch Switch States:

Manual Latch Release for Power Liftgate (PLG)
To manually open the PLG, due to power latch failure, remove the latch access cover located on the lower center of the liftgate trim panel. Reach in on the right side of opening, and push down on the manual latch release lever.

Unlatch/Cinching Motor
The latch uses a bi-directional motor to accomplish both release and cinch operations. The motor is driven in one direction to cinch and in the opposite direction to release.

During a cinch operation, power is supplied to the unlatch/cinching motor by the PLG module when the secondary latch position is reached during a power close operation. When the motor activates, it pulls the liftgate into the primary latch position. The PLG module removes power from the unlatch/cinching motor when the primary latch position is reached.

During an unlatch operation, power is supplied to the unlatch/cinching motor by the PLG module when a valid open command is received.

Sector Gear Switches
The sector gear open switch and sector gear close switch provide input to the PLG module in order to determine the position of the sector gear. The sector gear is part of the latch assembly. It is driven by the latch motor and in turn drives the latch mechanism. During a release operation, the PLG module deactivates the unlatch/cinching motor once the end of travel is reached. After a release operation, the PLG module keeps the latch released until the gate moves away from the vehicle. The PLG module then reverses the direction of the unlatch/cinching motor until the sector gear switches indicate the sector gear has returned to the neutral position. Refer to the following table for sector gear switch states:

Sector Gear Switch States:

The drive assembly consists of the following:

Position Sensor
When awake, the PLG module supplies a 5-volt reference voltage to the position sensor on a valid open command or anytime the liftgate is in the open position (up to 6 hours). The PLG module constantly supplies the ground. The position sensor has 2 data lines that the PLG module monitors to determine the liftgate movement and position. The PLG module uses the liftgate position information to determine which direction to power the liftgate (open or close) when a valid operation command is received. The movement is monitored to identify obstructions.

Actuator Clutch
The drive assembly actuator clutch separates the drive assembly actuator motor from the liftgate drive gear. This allows manual opening and closing of the liftgate without driving the motor. The PLG module supplies power to the drive assembly actuator clutch for any valid open/close operation. The clutch connects the drive assembly actuator motor to the drive actuator, allowing the motor to turn the actuator and open or close the liftgate.

Actuator Motor
The drive assembly actuator motor is a reversible motor. Upon a valid activation, the PLG module supplies power and ground to the motor circuits depending on the liftgate position and the direction the liftgate needs to be moved.

Power Liftgate (PLG) Control Switch - Instrument Panel
Pressing the instrument panel PLG control switch supplies a momentary ground signal to the PLG module which will open or close the liftgate depending on the conditions.

Power Liftgate (PLG) Rear Control Switch - Quarter Trim Panel
Pressing the PLG rear control switch (located on the LH quarter trim panel) supplies a momentary ground signal to the PLG module which will operate the liftgate depending on the conditions.

Exterior Handle Switch
When the exterior handle switch is activated, the SJB sends a signal to the PLG module which will open the liftgate depending on the conditions.

Remote Keyless Entry (RKE) Operation
The SJB receives a PLG activation command (double press) from the remote keyless entry (RKE) transmitter. The SJB will send a signal on the controller area network (CAN) to the PLG. The signal transmitted between the SJB and the PLG module is not specific to the open or close operation. The PLG module will determine which operation to carry out depending on the liftgate position when the signal is received.

Power Liftgate (PLG) Interface
PLG open operation requires the vehicle to be in PARK and the vehicle speed to be less than 5 km/h (3 mph). The PLG receives information over the CAN from the PCM for the PRNDL position and from the instrument cluster (gateway) for the vehicle speed. These inputs have network DTCs. If any vehicle speed sensor (VSS) or transmission range switch DTCs are retrieved and the PLG is not operating, repair these DTCs first.

Power Liftgate (PLG) Operation
The following is a brief explanation of a normal power open cycle of the PLG.
- The power open operation will begin with one of the following methods:
- The PLG receives a momentary ground signal from the PLG control switch.
- The SJB receives a signal from the remote transmitter key FOB (double button press).
- The PLG module receives a signal from the SJB indicating the exterior liftgate handle has been activated.

- The PLG module checks the PARK and VSS from the CAN communication link.
- The PLG module supplies power to the unlatch/cinching motor until the sector gear switches indicate end of travel which releases the PLG latch.
- The PLG detent switch, primary forkbolt switch and secondary forkbolt switch circuits are monitored for correct latch release signals.
- Power is supplied to the drive assembly actuator clutch and motor, opening the PLG.
- The PLG supplies power to the unlatch/cinching motor while monitoring the sector gear switches to return the sector gear to the neutral position.
- When the PLG is opening, the position sensor is monitored for liftgate position and velocity. If an obstruction is detected, the liftgate will stop.
- The PLG full open position is learned by the PLG module during the PLG initialization. When the PLG reaches the full open position, the PLG module removes the power from the drive assembly actuator motor and clutch.

The following is a brief explanation of a normal power close cycle of the PLG.
- The power close operation will begin with one of the following methods:
- The PLG module receives a momentary ground signal from the PLG control switch.
- The PLG module receives a momentary ground signal from the PLG rear control switch (LH rear quarter panel).
- The SJB receives a signal from the remote transmitter key FOB (double press).

- The PLG module checks the PARK and VSS from the CAN communication link.
- The PLG module will start an audible chime.
- After one second of audible chime, power is supplied to the drive assembly actuator clutch and motor as the audible chime continues 3 seconds total.
- As the PLG is powered closed, the position sensor is monitored for liftgate position and velocity. The PLG will reverse if an obstruction is detected.
- Also, as the PLG is powered closed, the pinch strips are monitored for a pinch condition. The PLG will reverse if an obstruction is detected by either pinch strip.
- The PLG detent switch, forkbolt primary switch and forkbolt secondary switch circuits are monitored for correct latch signals.
- When the PLG module receives switch signals indicating the secondary latch position is reached, power is supplied to the unlatch/cinching motor to pull the liftgate into the primary latch position. When primary latch position is reached, power is removed from the drive motor and clutch.
- When the PLG module receives switch signals indicating the primary latch position has been reached (liftgate is fully closed), the PLG module reverses the direction of the unlatch/cinching motor until the sector gear switches indicate the neutral position.

Power Liftgate (PLG) Chime
The PLG module requests a chime to sound for 3 seconds when:
- the PLG module receives a request to power close.
- the liftgate reverses when closing due to an obstacle.
- the liftgate stops opening due to an obstacle.

The PLG module requests a chime to sound for one second when an open or close input is received when:
- the vehicle speed is greater than or equal to 5 km/h (3 mph).
- the ignition key is in the RUN position and the transmission is not in the PARK position.
- the battery voltage is between 8 and 9.5 volts.

The chime will sound continuously for up to 5 minutes when the transmission is shifted out of the PARK position or the vehicle speed exceeds 5 km/h (3 mph) while the liftgate is closing. The chime will stop sounding when the liftgate reaches the latch, 5 minutes has elapsed or the transmission is shifted into the PARK position and the vehicle speed is less than 5 km/h (3 mph).

The chime will sound continuously for up to 5 minutes when the liftgate fails to close to the primary latch position after 20 seconds of powering in the close direction. The chime will stop if the liftgate reaches the primary latch position or 5 minutes has elapsed.

Power Liftgate (PLG) Initialization Procedure
If the PLG module loses the logic battery supply for any reason, such as battery disconnect, module disconnect or if left open for more than 6 hours, the PLG module will lose the PLG position stored in memory and will attempt to open when the liftgate switch is pressed the first time.

The PLG normal operation will not be restored until the PLG position is once again stored into memory. The initialization procedure is the learning process the PLG module uses to restore the PLG position in memory. The PLG module monitors the position sensor data received during the initial power open-and-close operation to learn the position.

Refer to Power Liftgate Initialization. Programming and Relearning

Power Liftgate (PLG) Awake/Sleep Status
- The PLG module is in the awake state whenever the ignition is in the RUN position.
- The PLG module is in the awake state while carrying out a close or an open operation, including cinch.
- The PLG module is in the sleep state when all of the following conditions exist:
- The latch is not in the fully unlatched position.
- The ignition is in the OFF position.
- No power operation is active.
- No wakeup inputs have changed state for more than 20 seconds.

- The PLG module is also in the sleep state when all of the following conditions exist:
- The latch is in the unlatched position.
- The ignition is in the OFF position.
- No power operation is active.
- No wakeup inputs have changed state for more than 6 hours.

The wakeup inputs for the PLG are:
- PLG open/close switch request signal
- Forkbolt primary signal
- Forkbolt secondary signal
- Detent switch signal
- Rear control switch
- Exterior handle switch
- Glass ajar switch
- CAN