RS6 Power Loss Issue Points to Limp Mode Problem

Had a similar issue with my 2012 RS4 last year, having some experience with performance cars and basic maintenance. When the check engine light came on and the car went into limp mode, I first connected a car diagnostic tool which showed multiple fault codes. Initially thought it was a sensor issue, but after taking it to a specialized workshop they traced it back to a problematic aftermarket tuning chip that was installed by a previous third-party tuner. The workshop had to completely reset the car computer and restore the original factory settings. The whole process took about 4 hours and cost me 180 Euro. After the fix, the power returned to normal and all dashboard lights cleared. To help diagnose your specific case, could you share: Has the car had any recent modifications or tuning work? Which specific fault codes is your diagnostic showing? When exactly did the power loss start? Does the power loss happen gradually or suddenly? This information would help determine if your issue is similar to what I experienced or something different.

Thanks for sharing your experience. My RS6 has 29173 KM and just had its service last month. Already checked with my auto scanner and got multiple fault codes pointing to the turbo system. Will definitely get those specific codes documented. The power loss started suddenly during highway driving and hasnt improved since. The check engine light came on at the same exact moment. The car computer seems to be limiting power output significantly. I havent done any modifications and everything is still stock from factory. Really helpful to know about your experience with the tuning chip issue. Since mine is completely stock, I am starting to suspect it might be related to the turbo system itself based on the vehicle diagnostics.

Based on your stock setup and those diagnostic codes, this sounds quite different from my tuning chip situation. After seeing your details about the sudden power loss during highway driving, it could indeed be turbo-related. Using my car diagnostic tool on my RS4 showed similar fault codes when I had a boost pressure issue last winter. The engine control unit often triggers reduced power mode to protect the engine when it detects irregular turbo operation. Common turbo system problems that match your symptoms: Boost pressure sensor malfunction, Wastegate actuator failure, Vacuum line leaks, Blocked air intake Since your scan tool already points to the turbo system, get the specific diagnostic codes documented. This will help pinpoint whether its a sensor issue or mechanical problem. In my case, the total repair cost for a faulty boost sensor was 350 Euro including labor. The good news is that modern engine management systems are quite protective, the reduced power mode prevents potential damage while you get it diagnosed properly. Given the low mileage on your RS6, this could simply be a sensor or actuator issue rather than a complete turbo failure.

Thanks for the detailed feedback. After looking at your suggested causes, I checked all vacuum lines and found no obvious leaks. I wrote down the specific fault codes from my car diagnostic tool: P0299 (Turbocharger Underboost) and P2263 (Turbo/Super Charger Boost System Performance). Given these engine issue codes and the sudden onset during highway driving, I am planning to take it to the workshop next week. The check engine light remains constantly on, and the reduced power mode is quite noticeable. Good to know about the protective nature of these systems, makes me feel better about driving it carefully to the shop. Since my RS6 is still relatively low mileage, I am hoping its just a boost sensor or wastegate actuator like you mentioned. Will update once I get the official diagnosis and repair cost. Really appreciate the detailed technical insights about the turbo system, helped me understand what I might be dealing with.