2008 Tahoe: The automatic back lift gate on my 2008 Tahoe stop...

Question edited for clarity and typos.
Question moved to model category.

Others report the same issue.

https://www.google.com/search?q=2009+Tahoe.+The+rear+lift+gate+open+on+its+own

Off the top of my head I would say the control module isn't functioning correctly

In link below of owners manual starting page 223 fuse box diagram I see two fuses for lift gate, one for module and the other is for logic.
https://cdn.dealereprocess.net/cdn/servicemanuals/chevrolet/2016-equinox.pdf
The link below problem found was switch in side vehicle was turned to off position.
https://chevroletforum.com/forum/tahoe-suburban-25/power-liftgate-stopped-working-36262/

https://www.youtube.com/watch?v=caThwc07PyU

https://www.youtube.com/watch?v=SdQuQyG78SI

https://www.youtube.com/watch?v=KbSAcgAzIZM
On video below it talk about adjustment of latch. If not opening right move latch around and attempt to open liftgate..
You might try closing latch with door open and push button to see latch open up. If it opens fine it could be binding when door is actually closed and latch needs adjusting.
https://www.youtube.com/watch?v=AmPIx4GuEkc

https://www.youtube.com/watch?v=nno-epcZxQc
https://www.youtube.com/watch?v=pBievVsXBLE

I have a 17 Terrain which does not have power lift gate. Something I notice in the video was if you have power lift gates it says to step back when opening and closing because there are sensors to prevent someone from being hit with the door.

Check the fuse marked ECC first and post back .

Your liftgate has obstruction sensors, if obstruction is detected in the power mode, the liftgate will reverse. Has a sensor on each side of liftgate. I don't know if replacing sensor/s will fix it, but, that would be my first thought. I hate to see you replace anything and it not fix it.
Your owners manual should give you info on lift gate operation. If you want my diagram for lift gate, holler and I'll post it.

Here is how it works !
Liftgate Locking Operation
The lift gate will lock any time the vehicle is shifted out of park on vehicles equipped with an automatic transmission and at vehicle speeds exceeding 5 kph with manual transmission. This happens in conjunction with auto door locks if enabled or independently of auto door locks if the feature is disabled. This ensures that the lift gate is locked anytime the vehicle is shifted out of park or when the vehicle is in motion.
The lift gate lock relay supply and coil sides receive a constant voltage through the battery voltage supply circuit and the ECC fuse. The normally closed contact is connected to ground and the control side is connected to the body control module (BCM). A lock function will occur when a door lock switch activation, keyless entry lock transmission, auto door lock function or a lift gate lock function has been received by the BCM. The BCM will then ground the control side of the lift gate lock relay. This energizes the relay and allows voltage to be applied to the lift gate lock actuator lock control circuit. Since the other side of the lift gate lock actuator is connected to the normally closed contacts of the door unlock relay to ground, the lift gate will lock. When an unlock function occurs the BCM will ground the control side of the unlock relay and the rear doors and lift gate will unlock.
The BCM also runs diagnostics on the lift gate lock relay control circuit and will set DTC B3825 as current and also send a Class 2 message to the DIC. The DIC will display REPLACE LIFTGATE FUSE to inform the driver that a fault has been detected in the lift gate lock circuit and that the lift gate is not locked. Faults that will set the DTC and cause the DIC to display the message could be any of the following:
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An open ECC fuse

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An open or short to ground in the lift gate lock relay battery positive voltage circuit

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A faulty lift gate lock relay

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An open or short to ground in the lift gate lock relay control circuit

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A short to ground in the lift gate lock actuator lock control circuit

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A faulty BCM

rear door hatch lock repair GMC Chevrolet - YouTube

? 4:26
https://www.youtube.com/watch?v=QS3PMhGgyAg
Apr 5, 2014 - Uploaded by auto resource
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chevy tahoe lift gate not opening - YouTube

? 2:12
https://www.youtube.com/watch?v=xU6ybiY3F4I
Sep 1, 2010 - Uploaded by 76bluemoon
Back lift gate/glass would not open or release. Even when unlocked with the key fob or the unlock switch on the drivers/passenger door. ... How To Install Replace Rear Lift Gate handle 2002-09 GMC Envoy Chevy Trailblazer ...

Yes. The gate is like any other door for the light system.

chevy tahoe lift gate not opening - YouTube

? 2:12
www.youtube.com/watch?v=xU6ybiY3F4I
Sep 1, 2010 - Uploaded by 76bluemoon Back lift gate/glass would not open or release. ... Wow, are you sure? .... known issue with tahoe, suburbans, hummers and othergmc vehicles. ... 2007-2012 Yukon Denali Rear Door Lock Actuator Replacement ... 2004 GMC Yukon XL rear liftgateremoval - Duration: 50:17. by Velvethamma 5,814 views.

I have a 2008 Suburban with the power liftgate disabled. I have had the power latch stop working, and the BCM report that the rear access open when it is closed (both gate and glass). Somehow the liftgate module thinks the gate is open, so I cannot open the gate at all, and the latch and rear wiper will not work. To reset the control module I pulled the liftgate fuse (#20) in the instrument panel fuse box, turned the car on, off, reinstalled fuse, turned car on, unlocked doors using drivers side switch, and the power latch will function again - at least for a while.