I have a frozen pipe in a wall.
The pipe goes from the basement to the 2nd floor
How do I thaw it without tearing the wall out?

1st of course hope that it has not cracked the pipe or you will have water in the wall after it does thaw.

At this point warming the room where the wall is, is about my only thought.

I have a frozen pipe in a wall.
The pipe goes from the basement to the 2nd floor
How do I thaw it without tearing the wall out?

If that pipe's cracked or split you're going to hafta open up that wall any how.
I would address this by opening a small hole in the wall near the floor line and shooting a hair dryer through the hole to warm the space up. Be on the lookout for moisture or the sound of running water inside the wall when it thaws out. If you have any of those shut the water off to the house quick. Good luck, Tom

I have this problem also and I have place a heat tape with a thermostate on it on the problem pipe and made sure that the wall is insulated. I plug it in when it is going down below 25 and so far it has worked for years. You must heat the pipe slowly and from the bottom where the freeze is so it will begin to drain and not burst your pipes.