Hey guys,

I have a CEL for code P0420 come on yesterday. I recently purchased a new Catalytic converter, a brand new one from a muffler shop, which works perfectly. I was originally running a test-pipe on the car and had my CEL light on for about 2 years. I am now wanting to sell the car, so I have placed a brand new catalytic converter on the car. My car was perfect a day ago, but after i hit about 135 miles after the new Catalytic converter was installed my CEL came on reading a code of P0420. Auto zone guy ran the OBD II on the car and stated it is the bank 1 o2 sensor. I can't imagine my CAT not working, since it is brand new. It is a bit odd though, I cleared the CEL and it hasn't come on and I am already at about 120 miles, is this normal or maybe a glitch? I rad on s2ki that someone ahd the same code and cleared it and it never came back, just curious to know what the issue is.

I don't want to purchase a brand new o2 sensor if this might be a glitch, could my o2 sensor have gone because of my test pipe that was on for over 2 years?

Any help or feedback is helpful, thanks!