2003 impala check engine light code P0420
 

I have spent a small fortune fixing various issues with this car. The current issue is that it will not pass inspection in Texass due to check engine light reappearing before drive cycle completes. It is always code P0420 & it always comes on while I am sitting at a ridiculously long red light. I'm running out of time and money to deal with this. If I have to replace the catalytic converter again, is there a particular brand I should look for? Also, is there possibly something else we're overlooking? From what I've read, this seems to be a common issue with this car. Thank you in advance for your help!

Did you also replace the O2 sensor?

hold old is the present cat

p0420 can set due to bad 02 sensors, bad cat.

if there is an issue with fuel trim control; it could shorten the life of the cat.

do not put on a cheap cat. cheap cats have low cerium content, the oxygen storing element in the cat. cheap cats will set the p0420 not long after installation.

Sorry if this ended up posting twice! I'm new here and not used to the setup yet. Yes, the 02 sensors were changed. It hasn't been a year yet since the cat was put on. That's why I was asking about a particular kind to use. Thank you for your help!