Audi Repair: Audi A6 LimpMode, audi a6, scan tool

Question
Hi
Just bought an Audi A6 1.8T Auto(triptronic). It was very slow to pull away. Called Audi garage and they advised the car is in limp mode. But there are no fault codes on the display i.e not even the gear information (linke PRND234) showing. When you switch the key to ON (without starting engine) ECP light is on. But if you start the car it goes off. Upon shifting to R or D it will give a hard jerk as well. I took it to a local garage and they connected some scan and said it is not communicating with ECU or something and they need to find short circuit to trace the fault. I am very confused as to what may be wrong with it. It's only got 60k on clock.
Please help me with your advise.
Thanks

Answer
hello
there may be some faults store in Trans. control module or ECM, this is the first to check , Most of the time display does not show anything . If the scan tool can't communicate with module - that's another problem. And that needs to be fix also.
Why?? - I do not know with out any faults . It may be one of 100 diferent problems. This needs to be checked in service.
good luck                             pltech