Cel p0421
 

Hey guys,

I drive a 2005 mazda 3 s hatchback with 59k miles.

I have had this code pop up on me twice now. I have read around and found that it is supposedly the pre-cat on the exhaust manifold. I got quoted a price of $220 to replace the manifold/pre-cat.

My question is should I waste time and money replacing the o2 sensors?

I am going to replace the spark plugs as well but I doubt that is what is triggering the CEL.

Btw, I can't take it to the mazda dealer because it has a rebuilt title, so any warranty is dismissed.

Thanks guys