How do i change the rear turn signal bulb on a 2009 buick enclave?

More than likely the problem in in the turn signal switch and not the flasher. But first, make sure that the bulbs are good. One bad one will keep the other from working, Using the emergency flasher, see if they are all working.

According to Wikipedia, 2009 to 2013 are the same transmissions

In its first year of production, the Enclave was often criticized for its 6-speed transmission, which was "hesitant to downshift."[7] For 2009, though, the powertrain is regarded as more competent with more abundant torque. For its entire production, it has been regarded as too heavy, weighing nearly 5,000 pounds (2,300 kg) with all-wheel-drive. Buick's VentiPorts have reappeared at the Enclave's introduction, a styling feature unique to Buick dating back to 1949.
Initial sales of the Enclave have been very strong, with demand far exceeding production capacity, forcing GM to add a third shift to the Delta Township plant.
With the arrival of the Buick Envision (which is slotted between the Enclave and Buick Encore) to North America in 2016 (for the 2017 model year), the Enclave will be bigger after Envision's debut, and the 2017 model year Enclave will be the last under the first generation platform.

Buick Enclave No Start Problems - Car Forums at Edmunds.com

forums.edmunds.com > Buick > Buick Enclave

Mar 1, 2009 - 31 posts - ‎13 authors
Learn more about Buick Enclave at the Edmunds.com Car Forums! Read real ... Time to take it in and see why car will not start with the remote key. Anyone else .... I drove my brand new 2011 Enclave yesterday. It sat for an ... Buick Enclave engine won't shut off. Parking brake light ...
5 posts
Aug 9, 2014
Buick La Crosse Stalling/Starting Problems
31 posts
Jul 26, 2006
More results from forums.edmunds.com

EnclaveForum.net: Won't start from time to time

www.enclaveforum.net > ... > Recalls, TSBs, FAQs, Links & How To's

Jun 23, 2008 - 20 posts - ‎16 authors
I have been having an issue of my Enclave not starting from time to time. If I turn the ignition back off and try again, sometimes it will start after the first ... 2011 Audi Q7; 2009 Audi A8L ... I usually just "flick" the key to let it auto-start and it normally works fine but ..... BUICK ENCLAVE Technical Service Bulletin EnclaveForum.net: 2013 BUICK ENCLAVE ...
20 posts
Aug 14, 2014
EnclaveForum.net: Car continues to run after key removed
20 posts
Nov 13, 2012
EnclaveForum.net: evaporation hose on gas tank - does ...
17 posts
Jun 25, 2012
EnclaveForum.net: Engine won't start low fuel level
12 posts
Feb 3, 2012
More results from www.enclaveforum.net

Did you check the bulbs?

Check that there is or was a recall on the lift gate switch. This is likely the issue but it did not get fixed.

Common lift gate issues:

AcadiaForum net

Remove the front wheel liner from the strut to the front bumper, all light assembly light bulbs will then be accessible. There may be screws however the majority is a plastic clip where you pull the center out then the clip easily removes.

per Gates Rubber Co. website, this is the routing diagram for a 2009 Buick Enclave V-6 3.6 L engine (i had to create an image from their book) the circle numbered 1 OR 2 will be the tensioner that you will need to release to get the belt on (you can usually use a ratchet with a short extension bar or socket to grab it to turn it away from the center) try VERY hard not to gall or damage the pulley or you will HAVE to replace it.

sounds like you got a bad bulb. turn the blinker on an step out to look at them. there should be a blown one.

Probabley just the bulb

I just watched the service station replace the rear turn signal bulb of our 2008 Enclave in about 5 minutes for $30! He opened the tail gate door, there were two small squares in the black lighting panel trim that he popped open. Inside each was a screw that he removed. This enabled him to remove the whole lighting panel. He then twisted the bad bulb and removed it and replaced with a new one. He checked that it was working then popped everything back into place added the screws and closed the squares back up. DONE!