P0420 & replacing the catalytic converter
I have an 03 530i that has the P0420 code that is popping and I need help with what to do. I have done some searching here on the forum and have not found the answer to my questions so I thought I would ask for help. A little history, I have had the car for 6 months and have had to do several things to it. The guy I purchased the car from listed several things that he knew were wrong. Six months later I think I’m to the end, but replacing the cat is what I’ve been avoiding, as it would be the most costly this far… The car has had multiple code over the last months, ie misfires – cam sensor, and I have worked on them one by one, down to this last one. I can give more specifics if its needed. P0420 is the only code that is coming up now. My questions are;
1. Does this mean that I need to replace the cat? I have replaced all the o2 sensors.
2. As this is bank 1 that is showing the error, can just that cat be replaced or do both need to be replaced?
3. If I need a new cat, what are some recommendations for an aftermarket cat that will work?
My goal at this point is to get it to a point that it will pass an inspection so I can sell it. Thanks for the help.