RS6 Catalytic Converter Failure Fix & Repair Costs

Had a similar situation with my 2006 A6 4.2 last year. Have some experience working on VAG cars, mainly doing basic maintenance and repairs. The symptoms you describe match what I encountered, check engine light, exhaust leak, and emissions system warnings. After seeing increased fuel consumption, I had my regular workshop run car diagnostics which confirmed the catalytic converter was failing. The NOx emissions were way above normal due to a crack in the catalyst housing. They found the leak during a thorough inspection of the exhaust system. Including parts and labor, the repair cost me 265 Euro for replacing the catalytic converter. The fix completely resolved the issues, no more check engine light, restored fuel efficiency, and proper emissions levels. To better assist with your specific case, could you share: Current mileage on your RS6? Are you noticing any performance issues or unusual sounds? Have you had any previous repairs to the exhaust system? Which specific error codes are showing up? This information would help determine if your situation matches what I experienced and whether a similar repair approach would work.

Last service was at 29500km where they did a full inspection. Since this catalyst issue started appearing right after, I suspect it may be related to something they missed. The check engine light triggered at 29792km. Running car diagnostics again revealed P0420 and P0430 codes consistently. I notice a distinct rattling sound from the exhaust system when cold starting, which seems to confirm internal catalyst damage. No previous exhaust repairs on record. Fuel efficiency has dropped noticeably, using about 2L/100km more than usual. Performance feels slightly down too, especially during initial acceleration. Based on the feedback about NOx emissions issues being resolved with catalyst replacement, I will get quotes for the repair. Would be great to hear more experiences specifically with RS6 catalyst replacements.

Reading about your RS6 symptoms reminds me exactly of what happened with mine. After seeing your latest numbers, I am even more convinced we faced the same problem. My RS6 had almost identical mileage when the catalyst started failing. The P0420 and P0430 codes match my experience perfectly. The rattling sound during cold starts is a telltale sign of internal catalyst breakdown, had the same noise until replacement. The increased fuel consumption of 2L/100km matches what I observed before fixing mine. Regarding the air quality and emissions system repair on my RS6, the total cost ended up at 890 Euro, significantly more than my previous A6 repair due to the higher-spec catalyst required. The NOx storage catalyst replacement completely resolved the rattling and restored proper exhaust flow. The repair eliminated all error codes and restored normal fuel consumption. Performance returned to factory specs, especially the initial throttle response you mentioned being affected. A word of advice from my experience: Make sure the workshop does a complete exhaust system inspection. My car had minor damage to the surrounding components that needed attention during the catalyst replacement.

Thanks for the clarification about the symptoms and timing. Those error codes do point directly to catalytic converter issues, and the timing right after the service is interesting. The fuel consumption increase you mentioned matches what others reported with failing NOx catalysts. The rattling during cold starts is particularly concerning since it suggests internal damage to the catalyst substrate. This tends to get worse quickly and can lead to complete catalyst failure if not addressed. After seeing similar symptoms resolved through catalyst replacement on other vehicles, I am going to move forward with getting repair quotes. Will focus on shops with experience handling performance exhaust systems given the RS6 specs. Most valuable has been learning about the typical repair costs and confirmation that replacing the NOx storage catalyst resolved similar symptoms for others. The exhaust system inspection tip is especially helpful, will make sure they check surrounding components during the repair. Planning to document the repair process and results to help others facing similar automotive repair challenges. Will update once I have some shop quotes and more concrete next steps for fixing the catalyst issues.