Corolla NOx Catalyst Aging Exhaust Leak

Sounds like a potential issue with your emissions system. Given the NOx catalyst code and exhaust smell, I'd guess you have a leak somewhere in your exhaust system before or near the catalyst. Have you checked for any obvious cracks or damage?

Thanks! I had a quick look but didn't spot anything obvious. Is there a specific area I should be focusing on?

Leaks can be tricky to find. Given the error code, pay close attention to the exhaust manifold and the pipe leading to the NOx catalyst. But honestly, with emissions stuff, best to get it properly smoke-tested at a workshop to pinpoint the exact location. It could be a small crack.

Turns out you were right, a small crack in the exhaust. Workshop confirmed it and replaced the section. Cost me 265€. Thanks for the help!