2005 chevy trailblazer liftgate ...gate tries to keep opening ...hear the motor

Door Lock System Components
The power door lock system consists of the following components:
• Driver Door Module (DDM)
• Passenger Door Module (PDM)
• Liftgate Module (LGM)
• Door lock relay
• Door unlock relay
• Body Control Module (BCM)
• Reversible door lock actuators in each of the doors
• LR/RR LOCKS 10A fuse (relay supply voltage)
• Door lock switches in driver and passenger doors (switches are integral components to the DDM and PDM)

Power Door Lock Operation
The power door lock switches are integral components of the DDM and PDM. The switches are two position normally open rocker switches. When placed in either the lock or unlock positions, the switches provide a direct input to the DDM or PDM. The DDM or PDM monitors these inputs and sends a Class 2 message indicating a change in the switch's respective position. Modules which activate the power door lock motors receive the Class 2 message and activate the motor in the appropriate direction to lock or unlock the vehicle's doors and liftgate. The modules which activate the power lock motors are:
• DDM (driver door lock actuator).
• PDM (passenger front door lock actuator).
• BCM (both rear door lock actuators).
• LGM (liftgate door lock actuator).

Could be a lot of thing's causing it not to work . The way we would diagnose is to hook up a scan tool an look for a DTC - diagnostic trouble code in the lift gate control module first ,no codes ,look at a wiring diagram an test voltages at the lock actuator ,switch etc... Also look on scan tool data to see if the lock/unlock command is getting to the lift gate module .

Door ajar switch possibly . The lift gate not working is a different matter . Could be any number of thing's .
Power Liftgate System Components
• Liftgate motor assembly
• Liftgate latch
• Liftgate module (LGM)
• Liftgate side upper sensor - left
• Liftgate side upper sensor - right
• Liftgate handle switch
• Liftgate close switch
• GMLAN serial data link
• PWR LIFT GATE 30 amp fuse
• PLG 10 amp mini-fuse

Your best bet take it to a qualified repair shop that has the diagnostic tool that can communicate with the lift gate control module , too check for DTC'S - diagnostic trouble code's .
Liftgate Module
The liftgate module controls the liftgate motor, liftgate clutch, and liftgate latch based on various inputs. The liftgate module also performs diagnostics on these inputs and outputs and will disable liftgate functionality and set DTCs should a fault be detected. The liftgate module is secured to the motor assembly at the left rear of the vehicle. The module requires a liftgate position learn procedure be performed when replacing. This allows the module to learn the full open and full closed positions of the liftgate.

DTC B153A 00: Liftgate Latch Switch Signal Circuit
DTC B153A 08: Liftgate Latch Switch Signal Circuit Signal Invalid
DTC B153B 02: Liftgate Open Switch Signal Circuit Short to Ground
DTC B153B 05: Liftgate Open Switch Signal Circuit Open
DTC B153E 02: Liftgate Position Sensor Signal Circuit Short to Ground
DTC B153E 05: Liftgate Position Sensor Signal Circuit Short to Battery or Open
DTC B153E 08: Liftgate Position Sensor Signal Circuit Signal Invalid

This is not a job for a diy'er or vehicle owner .

I would bet on the liftgate module (LGM) It controls all that stuff back there,wiper,defrost,gate ajar light,gate lock and unlock ect. Might try wiggleing the wiring boot where the wires go from the body to the gate,if it changes anything,bet on a broken wire inside that boot.
If not the LGM is my first thought.

There's a large torx screws hold it on. Cake

Likely a bad lock actuator in the lift gate.

If you look carefully you will find a manual release for it in the back. (You will have to crawl back there.)

It can be faulty switch or its issue with lift gate latch.Its got stuck up hard or cracked inside.It has to be inspected.-----------
There are few help links with proper solutions for these problem.I suggest you to refer the links.
Click the link below:----
2007 Mercury Mountaineer: Liftgate will not Unlock or Open? http://whoisbyme.blogspot.in/2012/06/2007-mercury-mountaineer-liftgate-will.html
------------
Adjust Hydraulic Lifters? http://schematicsdiagram.blogspot.in/2012/04/adjust-hydraulic-lifters.html
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How to open rear lift gate? http://repairhelpcenter.blogspot.com/2011/12/how-to-open-rear-lift-gate.html

--------- Power Liftgate Shuts Down http://whoisbyme.blogspot.in/2012/07/power-liftgate-shuts-down.html
------------ Power Lift Gate Will Not Remain Open http://whoisbyme.blogspot.in/2012/07/power-lift-gate-will-not-remain-open.html
----------- Power Lift-gate will not Operate http://whoisbyme.blogspot.in/2012/07/power-lift-gate-will-not-operate.html
------------- Liftgate will Not Stay Up Open? http://whoisbyme.blogspot.in/2012/07/liftgate-will-not-stay-up-open.html

---------------- Rear Door will not open http://whoisbyme.blogspot.in/2012/07/rear-door-will-not-open.html
------------ 2000 Toyota Corolla: Rear Door wont open from outside or inside? http://whatisbyme.blogspot.in/2012/05/2000-toyota-corolla-rear-door-wont-open.html

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These details will help.
Thanks.

The locking mechanism on the rear lift gate for the Chevy Uplander has some plastic and rubber-coated parts that can get jammed. If you can pull back the panel from the inside top near the glass, you can reach down and try to spray some silicone lubricant into the lock. This could help get those parts unstuck so they spring back when you pull on the handle latch from the outside. Once you get the rear hatch open, I recommend taking out the locking mechanism and thoroughly lubricating it. Your rear lift gate will start to release very easily from then on.

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.

try reseting it by undoing the battery cable