My A6 4.2 was stuck in limp mode so I ended up buying a new tcm. Before installing it I changed the output speed sensor + harness and it took the car out of limp mode. It is now stuck in 1st gear. I figured I would give the new tcm a shot since I have it on hand. I have heard I have to recode the ecu to accept the new tcm. Is this true? Can I do this using one of the cheap vag-com cables?