Liftgate Description and Operation
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Liftgate Description and Operation
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The power liftgate system consists of the following components:
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Driver door lock/window switch
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Power liftgate mode switch
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Liftgate outside handle release switch
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Liftgate shutface switch
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Liftgate latch assembly
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Left and right liftgate object sensors
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The power liftgate can be commanded to function in the following methods:
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An open/close command from the power liftgate mode switch
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An open command from the liftgate outside handle release switch
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A close command from the liftgate shutface switch
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An open request by a signal from the key fob to the remote control door lock receiver
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The liftgate module will respond to a request by commanding the liftgate latch to release the liftgate and commanding the liftgate pump motor to activate and pump hydraulic fluid to the liftgate control arm piston raising the liftgate to the open position.
The liftgate control module continuously monitors power liftgate operation and calculates its location and direction of travel from an external liftgate position sensor. One input returns the position of the liftgate relative to the x-axis and y-axis. The liftgate control module then uses these 2 inputs together to calculate its angle relative to the liftgate. When the liftgate mode switch is in the Garage position, the liftgate module will command the liftgate pump motor and monitor the x-axis and y-axis to stop the liftgate parallel to the vehicle roof.
The latch motor is a bi-directional motor and latch or unlatch operation is the result of the direction of the motor rotation. The liftgate module controls the latch motor through the control circuits by supplying power and ground in the appropriate polarity. The motor control circuits are monitored by the liftgate module prior to activation for a high or low condition and during motor operation for an insufficient current flow condition. The ratchet, pawl, and sector switches are part of the latch motor assembly and are used by the liftgate control module to determine the state of the latch during the process of latching or unlatching. Each of the latch switch signal circuits are supplied battery voltage through a resistor and monitored within the liftgate module. The latch switches share a common low reference circuit from the liftgate module and when the switch contacts close the signal circuit goes low and the liftgate module determines the switch to be active.
The handle switch and close switch are parallel circuits and provide a single input to the liftgate control module. The handle/close switch signal circuit is supplied battery voltage through a resistor and monitored within the liftgate module. The switches share a common low reference circuit from the liftgate module and when the switch contacts close the signal circuit goes low and the liftgate module determines the switch to be active.
The liftgate pump 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 pump motor through the control circuits by supplying power and ground in the appropriate polarity. The motor control circuits are monitored by the liftgate module prior to activation for a high or low condition and during motor operation for any irregular current flow conditions.
The power liftgate system uses an object detection method which consists of object sensors fixed to both sides of the liftgate near the seal area. The object sensors consist of an internal fixed resistor and normally open switch contacts which when closed will bypass the resistor. The signal circuit is supplied 5 V through a resistor and monitored within the liftgate control module, and during normal power liftgate operation the signal circuit should remain a fixed value. When an object presses one of the sensors the contacts close and the resistor is bypassed causing the signal circuit voltage at the module to go low.
