I have a 98 Honda Accord 4cyl. My check engine light and maint req'd light are on. I took it to AutoZone and they said it was returning a P0420 code. This means it is either the catalytic converter or the o2 sensor. Any ideas of which it could be? Has anybody had this error?

 

I have the same issue with a 2000 Civic LX that I put a LS swap in. I have a MagnaFlow High Flow cat on it. The code showed up and less than a week later the cat took a dump. Since it was under warranty I got another one put on and a month later the same code is back. I have noticed that the header is heating up really really fast and talked to some of my shop buddies and we think it is in the fuel mix. It's running rich or lean one of the two. I am getting the car hooked up to a scanner to find out what the car is acually doing and fix it as needed. When we figure it out I'll let you know what we did.