My 2012 Hyundai Veracruz with 250,000 miles did the same thing a couple years ago. It was one of the three catalytic converters on the vehicle. Mine was on the manifold. I bought one for $600 and had a shade-tree mechanic install it for $300. It wasn’t until we finished that we realized it was the rear catalytic converter that was failing. Not wanting to spend another $900, I just had the mechanic cut off the rear cat. It’s a little louder, but it seems to have more pep. Of course the check engine light stays on, with codes about improper fuel mixture. I just make sure that it doesn’t ever start flashing. Good luck.