06 A4 3.2 Tcm fault

[jacksonm3]

My olds mans car...Got the red prds light on the dash spoken to Audi and they have said not to drive it but has been driven!! it's currently at Audi waiting to be diagnosed still get all the gears but no sequential or sport can be used
Any ideas what this could be? thinking it could be the tcm if it is where is this located and can it be repaired as I'm dreading the cost of a new one from Audi

Cheers