P0420 - Help please.
So I've been riding around with this code for about a year! At first I cleared everything with my scanner, it came back. About 3-4 months ago I finally broke down and put in a new Magnaflow High Flow Cat. I ordered the wrong one apparently. Everything I read on this board and other places said for an 03 you want the cat with the O2 bung in it. Well, I should have gotten under and looked first. The O2 sensor is after the cat, further down the pipe on my car. The guy at the shop said he could just seal up the hole and weld it. He seemed to know what he was doing (I should have and would have ordered the magnaflow from him if I had found him first).
After about 2 weeks of driving with the new cat in, the CEL came on again! I figured, OK- the rear O2 is bad because of crap getting sent down the tube. So, I finally got around to looking at it this past weekend. I put in 2 new Denso O2 sensors and cleared the code. Everything was fine until yesterday. Now the light came back on. Checked the code- SAME code. What else could this be? Do you think I have a bad cat even though it'* new? I'm stumped.
Thanks in advance. Everyone here is a life saver!