RS4 Fuel Door Won't Open: Faulty Lock Actuator Guide

Had exactly this issue on my 2016 S5 last winter. The electric actuator that controls the fuel door completely failed, causing the release mechanism to stay locked. The cable release system was also affected since its integrated with the main lock actuator. The repair involved replacing the complete fuel door lock actuator assembly, including the electrical components and release mechanism. It was a serious repair since other electrical systems were affected, the central locking and trunk release also showed faults due to the electrical fault in the system. The technician had to remove the rear quarter panel liner to access the actuator. They found corrosion on the electrical connections which had caused the lock actuator to fail. The repair required special diagnostic equipment to reset the system after installation. This is not a quick fix job, the whole assembly needed replacement and proper programming. The electrical fault can spread to other systems if left unaddressed. Would recommend getting it checked soon since driving with a malfunctioning fuel door can be problematic, especially when needing to refuel. Based on the symptoms described, it sounds very similar to what happened with my car. The complete failure of the release mechanism combined with other affected systems typically points to a faulty lock actuator unit.

Thanks for your detailed explanation with the actuator replacement. Very helpful since my RS4 shows identical symptoms with the fuel filler release being completely dead. Quick follow-up, do you recall the total repair cost? Just want to get a rough idea before heading to the shop. Also, has the new actuator been working properly since the repair or did you notice any other quirks with the key fob or central locking system?

The repair job came to 210 Euro total, which covered replacing the lock actuator and fixing the defective linkage. Since getting it fixed at the mechanic, the fuel door release has worked flawlessly. The key fob and central locking are also functioning perfectly, no issues at all with any connected systems. The fuel filler door now opens smoothly every time I press the release button. Looking back, it was worth getting it sorted quickly to prevent any cascading electrical problems. The cable release system is also working as it should, which is important as a backup. What made the biggest difference was having the entire lock actuator assembly replaced rather than trying partial repairs. The new unit completely resolved those error codes you mentioned seeing.

Really appreciate the cost info and follow-up details. Just got back from the mechanic today and my experience was similar. Ended up paying 240 Euro for the complete fuel flap actuator replacement. The technician found the same corrosion issue you mentioned. The release mechanism works perfectly now when using both the interior button and key fob. They also cleared all the error codes and verified the central locking was working correctly. Such a relief to have it fixed properly this time. Glad I knew what to expect thanks to your advice. The mechanic confirmed replacing the entire electric actuator assembly was the right call rather than attempting partial repairs. No more struggling at the fuel station!