Learned something new today....
For those of you with tiptronic trans, if your PRNDL display blocks out and you have the inplausible signal DTC, here is something to check (for what it is worth, I seem to only run into this with the NB)...
The tiptronic switch asm uses HAL sensors and magnets. There are two magnets, a very tiny brick shapped one, a cyclinder shaped one. The cyclinder shaped one is in a little bracket that slides/snaps to a plastic carrier strip. What will happen is the bracket that holds the cyclinder magnet will pop loose and move back about 1mm, just enough to screw with you.
I had a brand new car with that DTC, my wiring tested out perfect. I order a new Tip switch and install... same issue. Hmmm... maybe I got a dud out of the box, order another switch... again, same problem. Turns out ALL THREE OF THEM had the same problem. I took the tiptronic switch asm all apart (simple, just snapped together) and put a dot of superglue on the cyclinder magent bracket and snapped it into place. Did this to all three of the tip switches, now they all work perfect.
So, before you run off and replace said switch, check that cyclinder shaped magnet, see if you can push it in (the bracket is kind of "wedge" shape), if you push in on it (towards the center of the asm), you should feel it click into place and the edge will be even/flush with the part it is fitted to.
You will understand this when you see if first hand. I should of snapped a pic but I forgot my camera.