C2 TT only revs up to 4000 (P, D sensor issue?)

Hi team my C2 Tiptronic recently showed an odd behaviour: Every other ride the engine will not rev higher than 4000 rpm, no matter if in P, N (standing) or D or M (driving) gear. It feels just hitting a rev limiter, there is no misfire whatsoever. When driving and shifting down (so that the RPM would go higher than 4000) the engine just slows down until it is below 4000, then it continues to run and accelerate normaly (until it hits the rev limiter at 4000). Besides all things work normally, the correct gear is shown in the dashboard. I understand that 996 with Tiptronic will not rev higher than 4000 in P or N to protect the gearbox (?). My hyothesis is that some kind of sensor does not detect that the gear D or M is selected, or P or N deselected. Did anybody experience this before? Where would such 'sensor' sit? Or is it the TT control unit?

Start with a diagnostic test using Durametric or PIWIS equivalent that can test all systems (ie. Tiptronic ect..) for fault codes ... With those symptoms there will surely be a fault code present in one of the systems that will lead the diagnostics in the right direction... Trying to correct the issue with any other process will be futile..

OK, good idea. Have ordered an iCarsoft Por 2 on Amazon - hope that show something. I do still however think that there is some sensor or so not working (similar to the reverse light switch). Not sure if the diagnostic tool would detect that..

Hi all, just for future reference: One ABS sensor was broken and thus the car thought it was standing still and did not let the engine rev > 4000 RPM. In other words: There is no sensor in the gearbox or so that let's the engine not rev > 4000 RPM, but the wheelspin needs to be >0.