Welcome to WAL. To start with, I don't see that having anything to do with the motor or old turbo. But as far as a code like that, it's up to you if you want to deal with it or live with it. It could be a number of things. But transmission problems don't usually fix themselves. The other tricky part is finding a good shop that can accurately diagnose it. From my experience, seems like a lot of transmission shops now days just want to put another unit in and be done with it.