Lexus ES NOx Catalyst Aging and Exhaust Leak

I had a similar issue with my ES. Check engine light and NOx catalyst errors. Definitely inspect your exhaust system thoroughly. A leak upstream of the catalyst can cause it to function improperly and trigger those codes. Any noticeable decrease in fuel efficiency?

Thanks for the tip! Fuel efficiency seems normal to me so far. Where exactly should I be looking for the leak?

Hard to say precisely without a proper inspection, but common spots are around the flex pipe and any connections before the catalytic converter. Given the NOx catalyst code, it's likely the leak is affecting the emissions system's performance and triggering the light. I'd advise taking it to a workshop, they will smoke test it and give you a definitive answer.

Alright, thanks for the advice. Took it to a workshop as you suggested and indeed there was a leak in the exhaust system. They replaced a section of the pipe, cost me 265€, and the error is now gone.