Problems with Seat Mii Diesel (model year 2019): Engine faults and weakening battery - tips and experience wanted

Hey, so I had a similar problem with my 2017 Seat Ibiza. And I'm really not a car mechanic, just a simple guy with a bit of car mechanic experience. When I took my car to the garage, it turned out that my engine control unit was faulty. The bill was, brace yourself, 1000 euros! But after that, everything ran smoothly again. To help you better, I need more information about your car. Do you drive a lot on long journeys or in the city? What is the current mileage? Any information could help us. Hope this helps you a little!

(Translated from German)

Thanks for the tip about the engine control unit, I hadn't even considered that. I have indeed driven a lot of short distances in the city. The current mileage of my Mii is 16536 km. The last time I had it serviced was recently. Maybe something went wrong there. Your bill sounds really scary, I hope it won't be that expensive for me.

(Translated from German)

Hey, no problem, I'm happy to help! With such a low mileage and mainly city driving, I would actually put the garage on the shortlist. Something may have been overlooked during the inspection or a part may not have been fixed properly. You can ask if they carried out a fault diagnosis and what the results were. But don't worry about the cost, the engine control unit was my personal super-GAU. It could also be something less dramatic, such as a defective sensor or faulty wiring, which would of course be much cheaper to fix. So don't panic! I would advise you to bring the car in for another check and refer to the symptoms you've noticed so far.

(Translated from German)

Thank you, that gives me hope. Alright, I'll take my car to the garage again and hope they find the fault. I will definitely mention everything you said. Thanks again for the help! Quite annoying all this, but I hope the car runs properly again soon.

(Translated from German)