RS6 Multiple Warning Lights Signal Troubling Issues

I had a very similar issue with my 2015 S6 last year. I have some experience working on cars but mainly routine maintenance, so diagnostic issues like this were beyond my comfort zone. The multiple warning messages were quite concerning, especially since they all appeared at once. After connecting my OBD-II scanner, it showed several fault codes related to the control module. The diagnostic scanner indicated the vehicle coding was incorrect, which explained why multiple systems were showing errors simultaneously. Took it to a workshop where they confirmed the coding issue. They had to reprogram and reset codes across multiple systems. The total repair came to 360 Euro, which included diagnostic time and the actual coding work. Based on your description, it sounds very similar, but to help further I would need to know: Are you getting any specific error messages you can share? Have you noticed any changes in how the car drives? Have you had any recent work done on the vehicle, especially anything involving the electrical systems? Do you have access to a scan tool to check the fault codes? Getting the actual fault codes would help pinpoint if your issue is similar to what I experienced or if its something else entirely.

Thanks for sharing those details. Used a scan tool yesterday to pull the codes and identified P0299 and P0234 turbocharger-related codes. After 162314 KM and my last service being just 2 weeks ago, these codes are surprising. Running engine diagnostics revealed inconsistent boost pressure readings. The check engine light started flashing during acceleration which matches the codes. Have tried clearing the OBD-II codes twice but they keep returning within minutes of driving. Given the recent service, wondering if something was overlooked or if the turbos are actually failing. Getting quotes between 2800 Euro-4200 Euro if replacement is needed.

Thanks for the follow-up. Your situation is actually quite different from my initial assumption about control module coding. When I had turbo-related codes on my S6, specifically P0299, it turned out to be a much simpler fix than a full turbo replacement. After seeing the fault codes return so quickly after clearing them with the scan tool, mine had the same behavior. The root cause was actually a split intercooler hose and a failing wastegate actuator, not the turbos themselves. Total repair cost was around 850 Euro including parts and labor. The timing near your recent service is interesting, worth checking if all hoses were properly reconnected and clamped. A loose connection post-service can trigger these malfunction indicator warnings. The flashing check engine light during acceleration is a telltale sign of boost pressure issues. Before accepting those high replacement quotes, request a smoke test of the intake system and a detailed inspection of the wastegate actuators. These fault codes often point to boost leaks rather than complete turbo failure. Have you noticed any whistling sounds or drop in power during acceleration? These symptoms helped diagnose my issue more accurately.

I appreciate that insight about checking for simpler issues first. Regarding your question, yes, there is a distinct whistle under acceleration that wasnt there before, and noticeable power loss especially above 3000 RPM. Based on the engine diagnostics and what you described, I will have them check the intercooler hoses and wastegate actuators before proceeding with any turbo replacement. The malfunction indicator seems most active during boost, which aligns with your experience. Already scheduled a pressure test and full system inspection for tomorrow. Your repair costs were much more reasonable than the quotes I received. The check engine warnings are concerning but hopefully its just boost leaks as you suggested. Will update once the OBD-II scan reveals more after the pressure testing. Makes sense to start with the simpler fixes before jumping to major repairs. Thanks for helping narrow down the potential issues.