Ok I've been posting trying to figure out what's wrong because tbh I don't know much about mechanics so I appreciate everyone's input and patience!

Ok so the problem code is P0748. I had known about it and was planning on fixing it but I fear that I waited too long because recently my car went into some kind of limp mode because it only uses 1 gear and D5 is flashing. I swapped a solenoid but it didn't fix it.

So really I just want to know if the transmission is kaput? Or is it likely that it can be fixed?
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Some wiring coming up from solenoid a is disconnected from the wire box at the 2nd wire so that could be it too?