Hi, I have rather limited knowledge of cars, but I experienced something similar with my 2015 Audi A3 diesel. The fault in my case was a short circuit in the control unit. The solution was a repair in my garage, which cost me 575 euros. As the details of your problem already show some similarities, this might be worth a look. But to give you more details and possibly better advice: Are there any other symptoms or issues you've noticed? This could help to better isolate the problem.

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Hey, thanks for your quick reply and the helpful information! There was actually another symptom that I noticed. Sometimes my engine warning light comes on, even though my Audi A4 was just serviced last week at 87750 km. Perhaps this is also connected. I will definitely take your tips into account and next time I go to the garage I will ask about a possible short circuit in the control unit. Hopefully the problem can be fixed quickly, 575 euros still sounds reasonable.

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Hello again! That's interesting about the engine warning light, there really could be a connection. In my experience with the Audi A3, there were also some warning lights on the dashboard at the same time as the key problems. Maybe there is a linked malfunction or the fault in the ECU is affecting multiple systems in your A4. However, before you go to the workshop, perhaps you have already tried changing the battery in your key? Sometimes this can also help. It's quite possible that your repair costs will be in a similar range to my A3. But as always, it depends on the specific diagnosis and the amount of work involved. I hope this helps you and good luck with your troubleshooting!

(Translated from German)

Hey, thanks again for your support! I haven't replaced the key battery yet, so I'll try that too before I go to the garage. The warning lights and the key problem at the same time sound really similar to my A4, so I really hope it's nothing serious. Of course, the costs are always an issue, but I'll just make a cautious calculation with an amount similar to yours. Well then, keep your fingers crossed that I get the whole thing sorted out quickly and as cheaply as possible!

(Translated from German)