Audi S3 Fuel Door Failure: Release System Breakdown

As someone with some repair experience, I faced a similar issue with my 2020 Audi S4 last year. The fuel door stopped responding both to the release button and manual release attempts. The problem turned out to be a defective lock actuator in the fuel door mechanism, combined with a worn linkage that had completely seized. The restricted vehicle functions you mention are typical when the system detects a fault in the fuel door circuit. My repair cost came to 210 Euro, covering both parts and labor. The workshop had to replace the entire fuel door mechanism including the lock actuator. The job took about 2 hours since they needed to remove some interior trim to access the mechanism. To help more specifically with your case, could you share: Does the fuel door make any sound when pressing the release button? Have you noticed any resistance when trying the manual cable release? Are there any specific error codes showing up? Did this issue start suddenly or develop gradually? These details would help determine if your issue matches what I experienced or if its something different in the electrical system.

Thanks for your response. My last service was at 55000 KM, about 3 months ago. The fuel door indeed makes no sound at all when pressing the release button. The cable release feels completely loose, offering zero resistance. The error code P3427 appears on the dash. The lock actuator issue started suddenly after a cold night. Before taking it to a workshop, I tried disconnecting the battery for 10 minutes hoping to reset the electric actuator system, but this didnt help. The key fob functions all work normally except for this issue.

Thanks for those details. Since our cars are similar, I can definitely confirm this matches my experience, especially with the lack of sound and loose cable. The P3427 code is exactly what my Audi showed before the repair. The sudden failure after a cold night is typical for a failed lock actuator, the cold can cause the mechanism to seize completely. The loose cable suggests the linkage has likely detached from the actuator, which is what happened in my case too. The battery reset attempt was smart, but when the lock actuator fails this way, its usually a mechanical failure that needs parts replacement. Since your key fob works fine for other functions, we can rule out any central locking system issues. Based on your symptoms matching mine exactly, youre likely looking at the same repair: replacing the fuel flap mechanism and lock actuator assembly. The good news is the repair is straightforward for a qualified workshop. Just make sure you have enough fuel before heading in, I learned that lesson the hard way when I couldnt refuel before the repair. Given your car is newer than mine was when it failed, this might even be covered under warranty. Worth checking your warranty terms before paying out of pocket.

Thanks for the detailed info and advice! Really appreciate the help narrowing down the cause. The matching error code and similar symptoms make me feel more confident about what needs fixing. The fact that yours started in cold weather too is interesting, definitely seems like the lock actuator is the culprit here. Good tip about having enough fuel before the repair. I checked and luckily have about half a tank left. I just called my dealer and since my car is under 2 years old, they confirmed this should be covered by warranty. They can look at it next week. Will update once its fixed in case the diagnosis turns out different, but sounds like I can expect a new fuel flap mechanism and lock actuator. At least I wont be facing that 210 Euro repair bill thanks to the warranty coverage. Really helpful to know what to expect when I take it in.