Hello, I'm Jason. I will do my best to answer your question quickly and accurately using the information you have provided.
Ok, so let me try to get some clarification here
When you say the converter doesn't lock up, do you mean that when you put it into gear, the car doesn't move at all unless you press the throttle?
If this is the case, it's not going to be a reprogramming issue
But a fluid check is absolutely necessary before trying to drive the car anywhere
and fluid change/filter replacement will require a few things
1) a method of monitoring fluid temperature during the filling process2) a fluid pump gun to fill it3) proper BMW fluid from a dealer
Now, if fluid level is correct, and you're still experiencing this problem, then a computer scan using a BMW-specific scanner is absolutely necessary to retrieve fault codes from the transmission computer
a generic OBDII scanner will NOT do this
This is a very good, consumer level BMW scan tool