Tundra NOx Catalyst Aging

I had a similar issue with my Tundra. Have you checked for any exhaust leaks? That was the culprit in my case.

An exhaust leak, huh? Where exactly was the leak on yours? I'll take a peek tomorrow.

It was a small crack near one of the catalytic converters, a common spot apparently. Honestly, you're probably best off taking it to a shop to get it properly diagnosed and repaired.

Thanks for the tip! Turns out it WAS a leak in the exhaust system, just like you said. Cost me 265€ to fix. I'm glad its finally fixed now!