Description And Operation

DESCRIPTION 

Courtesy of CHRYSLER GROUP, LLC

The power liftgate system is comprised of the following components:

1.	Refer to POWER LIFTGATE MODULE (PLGM) .
2.	Refer to POWER LIFTGATE DRIVE UNIT (PDU) .
3.	Refer to PINCH SENSORS .
4.	Refer to POWER LIFTGATE LATCH AND ACTUATOR  (Latch).
5.	Refer to POWER LIFTGATE LATCH SWITCH .
6.	Refer to POWER LIFTGATE LATCH AND ACTUATOR  (Actuator).

Other components of the system not shown:

-	Refer to OVERHEAD CONSOLE, D-PILLAR AND KEY FOB COMMAND SWITCHES .
-	Refer to CHIME  (integrated into the Power Liftgate Control Module).
-	Refer to BODY CONTROL MODULE (BCM) .
-	Refer to INSTRUMENT PANEL CLUSTER (IPC) .
-	Refer to RADIO FREQUENCY HUB (RFH) MODULE .

OPERATION 

The power liftgate system utilizes the PLGM. The PLGM contains all the solid state hardware and software used to control the power liftgate system.

Refer to COMPONENT INDEX .

Acts as the central gateway module for the CAN bus. It provides the following information to the PLGM

• vehicle speed
• shift lever or manual gear position
• longitudinal acceleration

The BCM is used to validate keyless entry requests on vehicle that are not equipped with keyless go.

Refer to COMPONENT INDEX .

The power liftgate chime can produce either single or repetitive, audible chime tones as an alert heard at the rear of the vehicle at the start of any power liftgate opening or closing cycle

The chime is completely controlled by and receives both a path to ground and current through hard wired circuits from the PLGM.

The PLGM outputs a Pulse Width Modulated (PWM) signal to drive the chime. When activated in the repetitive mode the chime is pulsed ON and OFF in 0.5 second intervals.

Refer to COMPONENT INDEX .

Used to display operation and warning information about the power liftgate system status to the driver.

Refer to COMPONENT INDEX .

OVERHEAD CONSOLE SWITCH - The overhead console switch is a momentary, push button actuated, resistor multiplexed switch. The switch has a path to ground at all times through an eyelet terminal secured by a screw to the body sheet metal within the passenger compartment. The switch provides a multiplexed output to the PLGM on a liftgate switch front signal circuit. The PLGM reads the switch output through an internal pull up. The output to the PLGM indicates whether the switch push button is depressed or released.

When the switch push button is depressed, it provides an Open  or a Close  request to the PLGM. The PLGM interprets the request based upon the present status of the liftgate. If the monitored status of the liftgate is not closed, the front switch input is interpreted as a Close  request. If the status of the liftgate is not opened, the front switch input is interpreted as an Open  request. If the switch button is depressed a second time, while the PLGM is in the process of opening or closing the liftgate, the PLGM will automatically reverse the liftgate to the full open position.

D-PILLAR SWITCH - The D-pillar switch is a momentary, push button actuated, resistor multiplexed switch. The switch receives source voltage from the PLGM through an internal pull up on a power liftgate logic return circuit. The switch then provides a multiplexed output to the PLGM on a liftgate switch rear signal circuit. The output to the PLGM indicates whether the switch push button is depressed or released.

When the switch push button is depressed, it provides a Close  request to the PLGM. If the push button is depressed a second time, while the PLGM is in the process of closing the liftgate, the PLGM will automatically reverse the liftgate to the full open position. This switch will NOT open the liftgate if it is already closed.

KEYFOB - If equipped with keyless go, when the RKE liftgate button of the FOBIK is depressed, the on-board transmitter of the FOBIK generates a high frequency RF request signal that is received and validated by the RFH module. If the RFH module determines the RF signal was generated by a FOBIK that is valid for the vehicle, the RFH module relays electronic request messages to the appropriate electronic modules in the vehicle over the Controller Area Network (CAN) data bus to invoke the PLGM to start the liftgate actuation request.

Refer to COMPONENT INDEX .

The motor, transmission and screw-drive portions of the power liftgate PDU provide the power and torque required to open or close the liftgate under most conditions.

The Hall effect sensors provide the PLGM with both a speed signal and a direction signal. These Hall effect inputs allow the PLGM to monitor and respond appropriately to any irregularities in liftgate travel and or operation.

The long, large diameter coil spring within the PDU is strong enough to assist in opening and, in combination with the gas-charged lift cylinder on the left side of the liftgate, will support the liftgate in any open position. The short, small-diameter spring provides an initial liftoff that moves the liftgate latch away from the latch striker after the power liftgate latch is initially released.

Refer to COMPONENT INDEX .

Vehicles equipped with a power liftgate, utilize a power cinch/release latch. This power liftgate latch performs the same function as a manual liftgate latch as well as the power cinch/release capability.

The power cinch/release latch function is made possible by a latch actuator attached to the top of the liftgate latch assembly. This latch actuator contains a small drive gear that meshes with the latch assemblies internal gears to perform the power cinch/release function. The latch actuator is controlled by the PLGM, which controls the cinch function and limits actuator current draw to protect the assembly. The latch is located in the lower center of the liftgate assembly and contains integral switches. These switches include, liftgate ajar, secondary, pawl, sector and power liftgate exterior handle.

Refer to COMPONENT INDEX .

When the exterior liftgate handle is pulled:

• a mechanical cable inside the liftgate activates the power liftgate release switch in the power liftgate latch assembly.
• a hard-wired signal is then detected by the PLGM.
• the PLGM then looks at the vehicle lock status on the Controller Area Network (CAN) data bus.
• if the vehicle is not locked and the operating conditions are met, the PLGM then applies power to the latch mounted motor, which moves the liftgate from the primary closed and latched position to the open and movable position.

Refer to COMPONENT INDEX .

The PLGM has the responsibility of authorizing the power liftgate operation requests.

Battery voltage is supplied to the Power LiftGate Module (PLGM) through a fused B(+) fuse in the Power Distribution Center (PDC) so the PLGM can operate regardless of the ignition switch status.

The PLGM monitors many hard wired switch and sensor inputs from the liftgate latch and cinch mechanisms, the PDU, the D-pillar power liftgate switch, the exterior latch handle power liftgate switch, the overhead console power liftgate switch and both pinch sensors.

The PLGM also confirms safety requirements are met before supplying power to the PDU to begin any power cycle.

The PLGM software detects obstructions through inputs from the two pinch sensors as well as by monitoring the resistance to travel of the PDU. When a sufficient obstruction is detected, the PLGM will reverse the direction of the liftgate. Also, an exterior liftgate handle pull during an automatic Close  cycle will reverse the power liftgate operation to Open  , while an exterior liftgate handle pull during an automatic Open  cycle will cancel the cycle and put the power liftgate into full manual operation.

The PLGM also monitors many electronic message inputs received over the Controller Area Network (CAN) data bus network. Electronic message inputs include: ignition switch status, Transmission Range Sensor (TRS) status, vehicle speed, Remote Keyless Entry (RKE) commands, vehicle theft alarm status, power lock system status and (if equipped) liftgate flip-up glass ajar switch status. In response to those many inputs, the PLGM logic allows it to properly control numerous hard wired outputs that operate the power liftgate latch and cinch mechanisms and the PDU that opens and closes the liftgate as well as the chime tone generator that provides audible indications of the power liftgate status. The PLGM will also place electronic messages on the CAN data bus indicating the liftgate status and many of the hard wired sensor inputs it receives for use by other electronic modules in the vehicle.

Refer to COMPONENT INDEX .

During a power liftgate "close" cycle, if either of the two conductive rubber strips (tapeswitch) of the pinch sensor come in contact with an obstacle, the pinch sensor circuit is completed. This tells the PLGM that an obstruction is felt. The control module will stop the liftgate immediately and return it to the full open position.

The thermistor portion of the right pinch sensor provides the temperature signal to the power liftgate control module (temperature is provided when the pinch sensor is in an unpinched condition; when pinched, temperature is unavailable because the thermistor is shorted). As the outside temperature increases, the resistance reading decreases. As temperature decreases, the resistance reading increases.

Refer to COMPONENT INDEX .

The RFH module is used to authenticate keyless entry requests on vehicles equipped with the keyless go system.