I would call gm regional, explain to them that your closest dealer has tried unsuccessfully 3 times to fix a different issue instead of doing the repair you researched on the internet that is proven successful. Then ask them which dealership you should take it to if you want it fixed correctly the first time.

Even go as far as telling the person the code and the relearn procedure. How much you spent at the dealership to not fix the problem, This way whomever they recommend if they don't fix it the first time you can call back and ask gm to get involved. (they may or may not). Or they will call the dealership you've been going to and ask them why they havent fixed the car.

it seems to need to be done with the gm dealer issue scan tool. so you are stuck with dealerships. I work on all my own stuff, if the manufacturer is going to design something that i, or a lot of independent shops, can not do, their dealership damn well better be able to do it right the first time.