VW Phaeton NOx Catalyst Failure & Exhaust Issues Fix

Had a very similar issue with my 2012 VW Passat diesel last year. From my experience with diesel engines and emissions systems, the symptoms you describe match what I encountered, especially the check engine light and those exhaust fumes. The NOx catalyst was indeed the culprit in my case, but it turned out the root cause was actually a minor leak in the exhaust system near the connection points. The repair shop found small cracks that were affecting the emissions system performance and throwing off the car diagnostics. Total repair cost was 265€, which included: Complete system inspection, Fixing the exhaust leak, Resetting the emissions system, Final testing to ensure proper nitrogen oxides reduction Before suggesting specific fixes, could you share: Current mileage on your Phaeton, Whether you notice any performance issues, What specific error codes you got, Any unusual sounds from the exhaust area These details would help determine if your issue matches what I experienced. Fuel efficiency might also be affected if its the same problem, so tracking your consumption could provide additional clues.

Thanks for the detailed information. My Phaeton had its last service at 121035km. The performance has noticeably dropped since these emissions system problems started. Im getting error code P2080 which points to NOx catalyst issues. The exhaust does make a slight rattling noise when cold. Fuel consumption has increased by about 2L/100km in the past month. The automotive repair costs you mentioned seem reasonable compared to what I was quoted. Since the air quality under the hood indicates possible exhaust leaks, I might have a similar issue with the exhaust system connections. Good to know this could be the root cause rather than immediately replacing the entire NOx catalyst. Would you recommend having the complete emissions system checked first before any parts replacement?

Thanks for providing those details, seems very similar to what I experienced with my Passat. The increased fuel consumption and error code P2080 match my symptoms exactly. Definitely recommend getting the complete exhaust system inspected first. In my case, fixing those connection leaks restored proper catalytic converter function and resolved the nitrogen oxides emission issues without needing major parts replacement. The car diagnostics should include: Pressure testing of the complete exhaust system, Inspection of all connection points and gaskets, Testing of the NOx sensor readings, Full emissions system performance check The rattling you mention when cold is particularly familiar, I had the same thing. It disappeared after the exhaust leaks were fixed, which also helped restore normal fuel efficiency. Given your mileage and symptoms, sounds like you might be dealing with the same exhaust system issue rather than a failed NOx storage catalyst. A thorough inspection could save significant repair costs compared to immediate parts replacement. Worth mentioning my fuel consumption returned to normal within about a week after the repair.

Thanks for the helpful responses. After comparing my situation with these similar cases, I feel more confident about how to proceed. The matching symptoms, especially the cold start rattling and increased fuel consumption, make me think my Phaeton likely has the same exhaust system connection issues. Ill schedule a complete inspection of the emissions system first, focusing on potential leaks near the catalytic converter and NOx catalyst connections. The car diagnostics should reveal if I can avoid the more expensive parts replacement route. Really appreciate the detailed breakdown of the repair process and actual costs involved. Will update once I get the exhaust system checked and know more about whats causing these emission problems. The possibility of a simpler fix is encouraging, especially since my symptoms align so closely with the resolved case shared here.