Liftgate will not stay open. When you push button it opens fully, but then immediately closes

go see a local mechanic .

Does it have a power lift gate ? Do you know anything about automotive electrical systems ? How to use a wiring diagram along with a digital volt ohmmeter to test electrical circuits . ?
Power Liftgate
The power liftgate feature will allow 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 liftgate movement. The power liftgate uses a power cinch system to latch the liftgate.
The power liftgate system consists of:

• Power liftgate control switch (located in the overhead console)
• Power liftgate motors (located in the rear headliner area)
• Optical sensor and power liftgate encoder wheel (located in the left power liftgate motor assembly)
• Pinch strip switches (located on the body by the liftgate)
• Home position switch (located on the cinch actuator)
• Forkbolt switch (located on the cinching latch assembly)
• Detent switch (located on the cinching latch assembly)
• Liftgate close chime module (located in a unit external from the power liftgate module)

The forkbolt and detent switch are located on the cinch latch assembly and the home position switch is located on the cinch actuator assembly. For information on removal of the latch or cinch actuator assembly, refer to Section 501-14 .
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 six 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. For additional information, refer to Power Liftgate Initialization .

Power Liftgate Initialization NOTE: If the power liftgate system is turned OFF in the message center, the system cannot be activated with any switches or with the liftgate handle. The system will need to be turned ON for any power operation to occur.
NOTE: 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 six 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.

1. Manually close and fully latch the power liftgate.

1. NOTE: If the power liftgate does not open during this step, refer to the symptom chart to diagnose the power liftgate for no operation. Power open the power liftgate by using the keyfob or overhead console switch.

1. Once the power liftgate is fully open, close the power liftgate by using the keyfob or overhead console switch.
2. your best bet mite be to have a qualified repair shop check it out .

An electronic control module controls it .
The liftgate module (LGM) controls operation of the liftgate latch motor and the liftgate actuator assembly. Do you have a Liftgate Ajar Indicator ON ? Or a message in the message center driver information center (DIC) illuminates the LIFT GATE AJAR indicator ? The liftgate control module could have a DTC - diagnostic trouble code in memory !

When open, the liftgate can be closed by either a keyless entry transmitter or the liftgate close switch. When a GMLAN serial data message or switch input is seen, the liftgate module begins the close sequence. The liftgate motor is reversed, lowering the liftgate until it latches into the liftgate latch. Once latched, the latch will cinch the liftgate to a fully closed position.
Power liftgate function will only be allowed if certain operating criteria are met. Any of the following may cause the power liftgate not to function:
?€¢ Vehicle is not in park. ?€¢ Engine cranking is present. ?€¢ Temperature limits have been exceeded. ?€¢ Liftgate motor overcurrent is detected. ?€¢ Excessive hall effect counts are seen. ?€¢ System voltage is out of range. ?€¢ A DTC is set that disables power liftgate functionality. The liftgate also receives inputs from 2 object detection sensors. If either of these sensors indicate an object is in the path of the liftgate, liftgate functions will be suspended until the object is removed.

Do you have power lift gate ?
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 six 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. For additional information, refer to
Power Liftgate Initialization NOTE: If the power liftgate system is turned OFF in the message center, the system cannot be activated with any switches or with the liftgate handle. The system will need to be turned ON for any power operation to occur.
NOTE: 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 six 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.

1. Manually close and fully latch the power liftgate.

1. NOTE: If the power liftgate does not open during this step, refer to the symptom chart to diagnose the power liftgate for no operation.
   Power open the power liftgate by using the keyfob or overhead console switch.

1. Once the power liftgate is fully open, close the power liftgate by using the keyfob or overhead console switch

Electronic's , aren't they great ? There is a control module (power lift gate module ) Switch (sensor) inputs to the module . Lift gate obstacle detection strip right and left , liftgate cinching motor ,liftgate unlatch motor .Liftgate drive motor assemblys left and right . Probably a bad switch feeding bad voltage signal to the control module ! Like one of the obstacle detection sensors maybe. Could possibly have DTC'S - diagnostic trouble codes stored in the control module. Your best bet maybe to have the dealer run diagnostic's on it , check for codes . Need a factory or professional type diagnostic tool to do this. I would say you mite be able to check the sensor inputs to the module , don't know what or how much voltage > Some of these circuit's are a five volt signal from the module . Ohm check the obstacle detection sensor ? I still think best thing would have it checked for DTC'S . Almost forgot about the thing opening when you close another door , All the modules on the vehicle are connected on what is call a serial data network . Doors have modules inside as well .could be commanding that door open some how.
If you would like to see what your up against , here is a web site for free wiring diagrams http://www.bbbind.com/free_tsb.html Enter vehicle info. year , make , model and engine size. Under system click on body & accessories , then under subsystem click on power liftgate. Click the search button ,then the blue link. The second diagram down starts liftgate diagrams . Good luck !

check the switch in the glove compartment

{: ) Your liftgate struts (shocks) could have gone weak. If it's a power liftgate, press the off button to disable the power liftgate function, so that you can open the liftgate manually. With a little help from you, extend the liftgate at full open position and check if it will hold itself up there as it normally should. If it starts to fall off as you catch it, that means the liftgate struts don't have enough pressure anymore to push and sustain the weight of the liftgate. Check for signs of leak on the struts, or better if you can replace it both.

To unlock the liftgate, press the unlock button on the Remote Keyless Entry (RKE) transmitter twice or use the power door lock switch.
To lock the liftgate, press the lock button on the RKE transmitter or use the power door lock switch. The liftgate does not have a key lock cylinder.
To open the liftgate, pull up on the handle located in the center of the liftgate.
When closing the liftgate, use the molded handles to pull the liftgate down. Push the liftgate closed until it latches.

POWER LIFT-GATE OPERATION - To open the optional power liftgate, push the button on the instrument panel , press on your five-button key fob (if equipped), or press and release the control located in the left rear quarter panel (Figure B). To unlatch the liftgate glass, push the button ) under the center of the license plate lamp shield, or press on your five-button key fob. Do not open the liftgate or the liftgate glass in a garage or other enclosed area with a low ceiling. Keep clear of the liftgate when operating the rear switch. To open the liftgate manually, pull the handle located on the liftgate to release the liftgate from the vehicle. The power system will take over when you release the handle. To close, make certain the rear window is closed, and then pull down the liftgate a few inches to activate power closing. Closing the gate rapidly or more than a few inches may activate the obstacle detection feature and stop the power system.------------ Also click this link for more help:--- http://technoanswers.blogspot.com/2011/05/power-liftgate-on-will-not-open-on.html ------------ This should help.Keep updated.Thanks.Helpmech.

Hold the hatch hard closed into its frame whilst pulling on the release handle. The mechanism on most cars consists a grab/release on the door and a simple metal hop at the bottom of the frame. Over time the hoop can become loose and move slightly inwards each time the door is shut. The door seal rubbers push back on the door surround putting a lot of tension against the grab/release mechanism preventing it from releasing. By pressing on the door and compressing the rubber surround you will take the pressure off the release mechanism and allow it to open when you pull on the handle. Once the door hatch is open, loosen the mounting bolts to the metal hoop and move it out about 10mm. Tighten the mounting bolts. Shut the door gently as a trial close and check for security of fit. If very slack, ease the hoop inwards a couple of millimetres. When happy, tighten the mounting bolts securely. draw around the hoop mount with indelible ink so if it moves in future you have early visual warning and can remount it easily