I had this message and have not found this solution in my search of forums etc so I will share it. It started as intermittent, became permanent and then it started holding on to the key because it said it was not in Park. The gear indicator lighting also behaved erratically. Fault code was P189000: Signal wire for Tiptronic Electrical error. I eventually found that the ground connections in the centre console were 0.5 to 5 volts above a true ground. This was preventing the Tiptronic and Park sensors from working properly. The ground point was failing, but was inaccessible without removing the whole console. I ran a new brown ground wire from a dashboard mounting bolt (accessible from the fuse box cover) to the cigar lighter connector. The studs holding the gearchange assembly were not reliable grounds.