VW Touran NOx Catalyst Leak Causing CEL Alert

Had the same problem with my 2017 VW Tiguan diesel. The exhaust leak started as a minor issue but quickly developed into a significant problem affecting fuel efficiency and overall engine performance. The initial symptoms matched yours, check engine light and emissions-related codes through car diagnostics. The leak was located at the connection between the exhaust manifold and the catalytic converter. The NOx catalyst had deteriorated due to the leak allowing excess oxygen into the exhaust system. In my case, a complete catalytic converter replacement was necessary as the internal honeycomb structure was damaged. The repair also required replacing gaskets and corroded bolts around the exhaust manifold. This was not a minor fix, the work took two full days due to the complex nature of modern diesel exhaust systems and their impact on air quality standards. Important to know: Continuing to drive with these symptoms risks further damage to other exhaust components and can lead to decreased engine performance. The sooner this gets addressed, the better chance of avoiding cascading problems with the DPF and other downstream components. Would strongly recommend getting this checked soon, as exhaust leaks tend to worsen rapidly in diesel engines, especially in vehicles with similar mileage to yours.

Thanks for sharing that experience. My situation was eerily similar with my 2020 Touran. The emissions system issues started exactly as you described and the car diagnostics confirmed problems with both the exhaust leak and nitrogen oxides readings. I especially appreciate the warning about potential damage to other components, as that helped me decide to fix it quickly rather than wait. I went ahead with the repair, but I am curious, would you mind sharing what the final cost was for your catalytic converter replacement and associated work? Also, have you experienced any other exhaust system problems since the repair?

Thanks for the follow-up. After getting my Tiguan repaired, the NOx emissions returned to normal levels and the exhaust system has worked flawlessly. The mechanic identified and fixed the aging NOx storage catalyst, which was the root cause of the elevated nitrogen oxides readings. In my case, I was fortunate that a complete catalytic converter replacement wasnt necessary. The repair focused on sealing the exhaust leak and addressing the catalyst issue, which came to 265€ total. This included labor and new gaskets. Much better than the potential cost of a full catalytic converter replacement. The automotive repair shop completed everything in one day, and I havent experienced any exhaust system problems in the past 18 months. The check engine light has stayed off and emissions readings are consistently within normal range during regular diagnostics. The quick action on your part should help avoid the more extensive damage I initially feared. Having a proper exhaust system repair done early typically prevents those cascading issues with other components.

I took your advice and went to get it checked right away. The mechanic found the exhaust leak was actually smaller than feared, but the NOx catalyst definitely needed attention. After a thorough automotive repair inspection, they determined a full catalytic converter replacement wasnt necessary. Instead, they fixed the leak, replaced some worn gaskets, and performed maintenance on the emissions system. The whole repair came to 320€, which was much better than I expected. The work took about 4 hours and the improvement in fuel efficiency was noticeable right away. The check engine light cleared up and my latest emissions test shows everything is back to normal. Air quality sensors are all reading correctly now. Really glad I didnt wait on this repair. The mechanic mentioned that catching these issues early prevented what could have been much more extensive damage to the exhaust system. No problems since the fix three months ago.