I thought the federal emission warranty was 8 years or 80,000 miles. 122k probably puts him out of any warranty, even if I'm wrong about the warranty limits. Definitely sounds like they put a bad cat on though- not that the cat is necessarily broken, just not adaequate.
There's also a possibility that your o2 sensor could be the culprit. Try switching the rear one to the front and see if you still get the same code. If so, it's the cat. If not, it's the o2 sensor.
There's also a possibility that your o2 sensor could be the culprit. Try switching the rear one to the front and see if you still get the same code. If so, it's the cat. If not, it's the o2 sensor.
