Safrane NOx Catalyst Exhaust Leak

That sounds frustrating! I had a similar issue with my old Opel Vectra: check engine light, emissions problems... Could an exhaust system leak cause your NOx catalyst to age prematurely? What does the error code say specifically?

The error code points to the NOx catalyst efficiency being below the threshold. You mentioned your Vectra. What was the problem for you, and how did you pinpoint it to the exhaust system?

My Vectra had a cracked exhaust manifold. The leak messed with the oxygen sensor readings, which affected the catalytic converter's performance. NOx values were high when I got the error code. I’d advise taking it to a workshop to be sure that is the problem!

Thanks for the tip! I took it to the shop, and you nailed it. A small crack in the exhaust, right before the catalyst. A new pipe section and a fresh gasket later, and the error is gone! It cost me 265€, but it's worth it.