How to fix P189C problem

P189C is a problem with your transmission which can't build up enough pressure. You should check your fuses first. Unfortunately I can't tell you which fuses you have to check, but I think it was a 30A fuse. If all of them are undamaged it may be a problem with some faulty wiring, bad connections or even the whole Mechatronic Unit. But even if you find and fix the problem yourself, you still need to clear the faults from your transmission control module so it is advisable to visit an authorized service station.