S6 Avant Transmission Control Module

Transmission Control Module
I have a 2002 S6 Avant with a transmission issue -- the car shifts into limp mode, but still drives - albeit very slowly w/o and torque. The P R N D S line is completely RED in the center cluster.
I have received two opinions from Audi certified mechanics - one, the worst case scenario - the transmission is shot & the second is that it is the TCM - transmission control module - that is bad. The TCM is located underneath the passenger footwell carpet - must also remove seat to access this.
-- Does anyone here know how to further diagnose whether the transmission is shot before I go down the TCM route (its an expensive 'try' - parts and labor to check it will come close to $1000.00 and part is not refundable) THANKS!

First you need a scan of the TCU, preferably with Vagcom or from a dealer to get an idea of the faults. Secondly, are you sure the seat has to be removed and the footwell carpet can't be just pulled back along with removing the trim piece where the carpet meets the door seal? HP24 was never a great transmission but there are some reputable rebuilders that do a good job, one of them is Tozo from Audizine and someone here probably has his E-mail or #, he's located in Chicago area.

You don't have to remove the seat. TCM most likely had taken a swim. Take it out, have a look.

f125 maybe? you need to scan with vcds to see..