Seat Arosa automatic transmission problem

Sounds like a nasty problem. The symptoms you're describing with the implausible shifting, slipping gears, and grinding noises, coupled with the electronic display malfunction and stored error code, really point towards a potential control unit failure. Have you checked the wiring harness and connections to the gearbox and the shift knob? A loose or corroded connection can sometimes cause similar issues. Also, have you scanned the TCM (Transmission Control Module) for specific error codes? Knowing the exact code would help narrow down the culprit. A defective sensor could also feed bad data to the TCU and produce these symptoms. Be cautious though, as continuously driving with these issues could cause further damage to the gearbox. Before throwing parts at it, it would be beneficial to do some data logging to examine the sensor values and TCU commands while driving.

Thanks for the detailed reply. I haven't checked the wiring harness itself, just the connections. When you mention data logging, what parameters should I be monitoring specifically in the transmission control module?

Alright, if you've already checked the connections, it's less likely to be a simple wiring issue, although a thorough inspection is never a bad idea. Regarding data logging, focus on these parameters: Input Shaft Speed Sensor, Output Shaft Speed Sensor, Gear Selector Lever Position, Solenoid Valve Duty Cycles, Transmission Fluid Temperature. Compare these values to the expected ranges for each gear. Any inconsistencies or erratic readings could indicate a sensor problem or internal transmission damage. However, the symptoms you're experiencing are quite severe, and the fact that the gear selection display is also malfunctioning makes me strongly suspect the control unit is indeed the prime suspect. Given the potential for further damage and the complexity of diagnosing these systems, I would cautiously recommend taking it to a reputable workshop with experience in automatic transmissions.

Thanks for the detailed insights. It does sound like the control unit issue you described is spot on. I'll book it in with a workshop to get it checked out and sorted.