Kannu

My parents A3 threw an exhaust related fault code which was found to be caused by a faulty turbo. In this phase all worked.

The car was then driven to the service and they changed the turbo. After this they haven't been able to connect via OBD to the car (trying to Set The adaptations for the new turbo). They have tried 2 different systems (vcds and some other) and both don't work. The car powers up normally as far as they told me.

So something obviously happened during the install but nobody knows what.

Things that come to mind first are fuses and wires... In some thread there was a mention about a common broken wire in the loom that rubs battery housing.

Any other ideas how to continue?