GX Transmission Control Unit Failure

That sounds frustrating. I had a similar issue with my old Audi A6. The symptoms, especially the erratic shifting and display malfunction, remind me of when the transmission control unit went haywire. It's like the brain telling the gearbox to do one thing, and the gearbox doing another – a complete communication breakdown. Was there anything specific that triggered this or did it just happen?

Good analogy! It happened suddenly – one moment it was fine, the next, total chaos. The 'brain' is a great way to describe it. When you say 'transmission control unit,' is that buried deep in the gearbox or more accessible? Do you recall what pinpointed the problem on your Audi?

On the Audi, the control unit wasn't inside the gearbox, but mounted externally, though still pretty close. The garage diagnosed it by systematically checking all the wiring and sensors associated with the transmission. The error codes were a clue, but it took diagnostics to confirm it. I'd advise against trying to fix this yourself unless you're a seasoned auto electrician. Given the symptoms and error codes, it sounds like a defective control unit, which will probably need to be replaced. Time to take it to a reputable workshop.

Sounds like I'm out of my depth. I appreciate the insights; you've confirmed my suspicions. Just got a quote from the dealer: 1000€ for a new control unit and installation. Thanks again for the help.