2001 passat variant 1.9 tdi with tiptronic transmission.

Hello, An old teacher of mine would have called this a gremlin. Reason being is that at first glance the problem doesn't present itself. However, after scanning the vehicle, especially with live data from a test drive where the engine and transmission reach full operating temperature, the problem will offer clues that can be helpful in diagnosis. The ABS system does use a couple of sensors from the transmission to correlate wheel speed with vehicle speed, and heat can cause sensors to expand, creating inefficiencies. Your first step is to read the codes from your vehicle with a code reader that is able to contact the ABS control module as well as the transmission control module. That will likely give you at least a basic understanding of why the vehicle has placed itself into lim mode.