Power Liftgate System

The rear gate module continuously monitors power liftgate operation and calculates its location and direction of travel from an liftgate position sensor (part of the power assist actuator). One input returns the position of the liftgate relative to the x-axis and y-axis. The rear gate module then uses these 2 inputs together to calculate its angle relative to the liftgate. The liftgate release switch contains resistors which will incrementally drop the voltage level in the signal circuit as the switch rotated from the OFF position to the 3/4 position or the MAX position, the rear gate module will detect the change in voltage and will monitor the x-axis and y-axis as the liftgate is in motion to stop the liftgate parallel to the vehicle roof if the liftgate release switch is in the 3/4 setting or to open fully if the rotary switch is in the MAX setting.

The S45B Liftgate Release Switch has a push button switch to command the liftgate to open and close. The K9 Body Control Module monitors the voltage level on the open/close signal circuit, when the switch is not being pressed the voltage level is at 7.5 volts. When the switch is pressed a contact within the S45B Liftgate Release Switch closes providing a ground path for the signal circuit causing the voltage level to drop to near zero volts. The K9 Body Control Module will detect the voltage drop and will send a serial data message to the K194 Rear Gate Module to command the liftgate to open or close depending upon the current state of the liftgate at the time the switch is pressed.

The liftgate latch is a bi-directional motor and latch or unlatch operation is the result of the direction of the motor rotation. The rear gate module controls the liftgate latch through the control circuits by supplying power and ground in the appropriate polarity. The motor control circuits are monitored by the rear gate module prior to activation for a high or low condition and during motor operation for an insufficient current flow condition. The unlatch, primary, and neutral switches are part of the liftgate latch and are used by the rear gate module to determine the state of the latch during the process of latching or unlatching and will send the status of the latches to the body control module which is used to determine if the liftgate is closed or ajar. Each of the latch switch signal circuits are supplied battery voltage and monitored within the rear gate module. The latch switches share a common low reference circuit from the rear gate module and when the switch contacts close the signal circuit goes low and the rear gate module determines the switch to be active.

The K9 Body Control Module monitors the voltage level on the rear closure handle switch open signal circuit, when the liftgate handle switch is not being pressed the voltage level is at 7.5 volts. When the switch is pressed a contact within the rear license plate lamp module closes providing a ground path for the signal circuit causing the voltage level to drop to near zero volts, the body control module will then send a serial data message to the rear gate module to command the liftgate latch to activate.

The liftgate close switch signal circuit is supplied battery voltage by the rear gate module. The switch shares a common low reference circuit from the rear gate module and when the switch is pressed the contacts close and the signal circuit goes low, the rear gate module will detect the voltage drop and will send a serial data message to the body control module requesting the rear gate close request.

For vehicles without the optional passive keyless entry, when the liftgate handle switch is pressed, the body control module will check the status of the vehicle door locks. If the vehicle doors are locked, the body control module will ignore the signal from the liftgate handle switch. If the vehicle doors are unlocked, the body control module will permit the liftgate to unlatch and power open when the liftgate handle switch is pressed.

For vehicles with the optional passive keyless entry system, the body control module monitors the proximity of the keyless entry transmitter. If the exterior liftgate release switch is pressed and the keyless entry transmitter is within range, the body control module will send a serial data message to the rear gate module and will permit the liftgate to unlatch and power open. If the doors are locked and the keyless entry transmitter is not within range, the body control module will ignore the signal from the exterior liftgate release switch and the liftgate will not power open.