Opening liftgate on 2009 Cadillac STS Exterior Handel quite opening gate

limited info generic answer --check fuses relay and connections --will need to remove panel to access latch to inspect for damage or disconnected linkage

Try cleaning the contacts of the lock mechanism at the lift gate.

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 .

Has to have it .
Liftgate Trim Panel Plug
Procedure
From inside the vehicle lower the second and third, if applicable, row seats.
Use a small flat-bladed tool to remove the access plug from the liftgate lower interior trim panel.
Push on a silver lever located on the right just through the access hole to unlock the liftgate.
Open the liftgate from the outside of the vehicle using the exterior handle.

Outlook Traverse Acadia Enclave Lift Gate Won Open

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 the following:

• 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)
• There are a lot of electrical switches an motors
• Visual Inspection Chart Mechanical Electrical
  • Power liftgate motors
  • Power cinching latch and linkage
  • Power liftgate pinch strip switches
  • Liftgate and liftgate hinges
  • Liftgate assist cylinders
  • Liftgate strikers
  • Exterior release handle and linkage
  • Liftgate weatherstrip
  • Liftgate alignment to body and striker
  • Central junction box (CJB) fuse:
    • 5 (7.5A)
    • 105 (30A)
  • Power liftgate control switch
  • Wiring harness
  • Connectors
  Are you willing to take the back hatch apart to test this ,to find a fix . But first have it check for DTC'S - diagnostic troulbe codes '
• Power Liftgate Module Diagnostic Trouble Code (DTC) Index
  Power Liftgate Module Diagnostic Trouble Code (DTC) Index DTC Description Source Action B1342 ECU Is Defective Power Liftgate Module INSTALL a new power liftgate module. REFER to Power Liftgate Module in this section. B2477 Module Configuration Failure Power Liftgate Module REFER to Section 418-01 . B2522 Vbatt1 Circuit Failure Power Liftgate Module Go To Pinpoint Test B . B2552 Vbatt2 Circuit Open Power Liftgate Module Go To Pinpoint Test B . B2698 Vbatt2 Circuit Failure Power Liftgate Module Go To Pinpoint Test B . B2699 Left Pinch Strip Open or Short to Battery Power Liftgate Module Go To Pinpoint Test B . B2700 Right Pinch Strip Open or Short to Battery Power Liftgate Module Go To Pinpoint Test B . B2701 Left Pinch Strip Stuck Active Power Liftgate Module Go To Pinpoint Test B . B2702 Right Pinch Strip Stuck Active Power Liftgate Module Go To Pinpoint Test B . B2703 Open/Close Switch Stuck Active Power Liftgate Module Go To Pinpoint Test B . B2704 Optical Sensor Power Short to Ground Power Liftgate Module Go To Pinpoint Test B . B2705 Optical Sensor 1 Input Not Active During Powered Gate Movement Power Liftgate Module Go To Pinpoint Test B . B2706 Optical Sensor 2 Input Not Active During Powered Gate Movement Power Liftgate Module Go To Pinpoint Test B . B2709 Gate Open Output Short to Battery Power Liftgate Module Go To Pinpoint Test B . B2710 Gate Close Output Short to Battery Power Liftgate Module Go To Pinpoint Test B . B2711 Gate Open Output Short to Ground or Open Power Liftgate Module Go To Pinpoint Test B . B2712 Gate Close Output Short to Ground or Open Power Liftgate Module Go To Pinpoint Test B . B2713 Unlatch Output Short to Ground or Open Power Liftgate Module Go To Pinpoint Test B . B2714 Uncinch Output Short to Ground or Open Power Liftgate Module Go To Pinpoint Test B . B2715 Cinch Output Short to Ground or Open Power Liftgate Module Go To Pinpoint Test B . B2718 Gate Ajar Output Short to Battery Power Liftgate Module Go To Pinpoint Test B . B2721 Gate Ajar Output Short to Ground or Open Power Liftgate Module Go To Pinpoint Test B . B2722 Open/Close Switch Active During Self-Test Power Liftgate Module Go To Pinpoint Test B . B2723 Glass Position Switch Active During Self-Test Power Liftgate Module Go To Pinpoint Test B . B2724 Forkbolt Switch Invalid During Self-Test Power Liftgate Module Go To Pinpoint Test B . B2725 Detent Switch Invalid During Self-Test Power Liftgate Module Go To Pinpoint Test B . B2726 Home Switch Invalid During Self-Test Power Liftgate Module Go To Pinpoint Test B . B2819 Gate Motor Circuit Short to Battery Power Liftgate Module Go To Pinpoint Test B . B2820 Gate Motor Circuit Short to Ground or Open Power Liftgate Module Go To Pinpoint Test B . B2821 Cincher Motor/Unlatch Actuator Short to Ground or Open Power Liftgate Module Go To Pinpoint Test B . B2822 Cincher Motor/Unlatch Actuator Short to Battery Power Liftgate Module Go To Pinpoint Test B . B2825 Movement Ceased Due to Excess Speed Deviation Power Liftgate Module Go To Pinpoint Test B . B2903 Chime Output Circuit Short to Battery Power Liftgate Module/ Liftgate Chime Module Go To Pinpoint Test C . C1935 Chime Circuit Failure Power Liftgate Module/ Liftgate Chime Module Go To Pinpoint Test C . U1950 UBP Communication BUS Fault UBP Communi- cation REFER to Section 418-00 . U2338 Invalid ACM Message Data Power Liftgate Module REFER to Section 418-00 . U2242 Invalid 4WAS Message Data 4WAS Module REFER to Section 308-07A . U2403 Invalid CSM Message Data Vehicle Security Module REFER to Section 418-00 . U2406 Invalid IC Message Data Instrument Cluster Module REFER to Section 413-01 . U2469 Power Liftgate Disabled By Customer Interface Instrument Cluster Module Turn power liftgate on at message center. U2470 Unexpected Keyfob/Keypad Button Press Power Liftgate Module Go To Pinpoint Test A . U2471 Unexpected PRNDL State Power Liftgate Module REFER to Section 419-10 . U2472 Unexpected IGN State Power Liftgate Module REFER to Section 418-00 . U2473 Unexpected Vehicle Speed Instrument Cluster Module/ Powertrain Control Module REFER to Section 413-01 . U2528 PRNDL Data Mismatch Power Liftgate Module/ Instrument Cluster Module Go To Pinpoint Test D .

Open the liftgate. Remove the liftgate applique. Refer to Liftgate Applique Replacement in Body Rear End. Remove the back up lamp socket (1) from the liftgate applique by turning the socket (1) counterclockwise. Remove the back up lamp bulb from the socket.
Lift gate Applique Replacement
Remove the lift gate trim panel. Refer to Lift gate Trim Panel Replacement .
1
Lift gate Applique Nuts (Qty: 5)
Tip
Disconnect the electrical connector.
Tighten
10 N?·m (89 lb in)
2
Lift gate Applique

Is the arms bent

It's now a recall item. See below.


NHTSA CAMPAIGN ID Number: 15V415000
Component: STRUCTURE:BODY:HATCHBACK/LIFTGATE
Manufacturer: General Motors LLC
Potential Number of Units Affected: 686287

Year: 2009
Make: Chevrolet
Model: Traverse
Manufactured
from: 2008-07-06
to: 2012-02-29
Recall Date: 2015-06-30
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Summary:

General Motors LLC (GM) is recalling certain model year 2008-2012 Buick Enclave vehicles manufactured January 3, 2007, to February 29, 2012, 2009-2012 Chevrolet Traverse vehicles manufactured July 6, 2008, to February 29, 2012, 2007-2012 GMC Acadia vehicles manufactured September 15, 2006, to February 29, 2012, and 2007-2010 Saturn Outlook vehicles manufactured August 17, 2006, to March 18, 2010. The affected vehicles, equipped with the power liftgate option, have gas struts that hold the power liftgate up when open. These struts may prematurely wear and the open liftgate may suddenly fall.

If the open liftgate unexpectedly falls, it may strike a person, increasing their risk of injury.

GM will notify owners, and dealers will update the software for the power liftgate actuator motor control unit so that the motor will prevent the rapid closing of the lift gate, free of charge. Owners were mailed interim notices on August 3, 2015. Owners will receive a second notice when remedy parts become available. Owners may contact Buick customer service at 1-800-521-7300, Chevrolet customer service at 1-800-222-1020, GMC customer service at 1-800-462-8782, and Saturn customer service at 1-800-553-6000. GM's number for this recall is 15240.

plug on inside panel of lift gate remove plug and use screwdriver to push on release use light in plug hole

The easy part is you just need the latch for the liftgate. The hard part is getting to it and opening the liftgate to replace the latch. You should be able to pull the liftgate trim off most of the way with the gate closed and try to manually actuate the latch to open the gate. You may have to go so far as breaking the latch from the inside to open the gate and then replace your latch.