Getting error code PO421 - Warmup Catalyst, Bank , Deficiency below threshold. Does this mean the Cat bt the manifold needs replaced, o2 sensor or something else?
Or if you get sick of the smell gut the cat or get an obx header which deletes the precat you should still pass an emissions test with the main cat but regardless to get rid of the code either do the non fouler method for 15-20 bucks or pay 400+ for a new precat
Lets not get ahead of our selves.. First check your 02 sensors to make sure they are operating correctly, If they are good then its the CAT. I recommend getting and after market CAT or just gut the whole manifold and CAT and get a header and do the old non fouler trick to the down stream o2 sensor. I personally find the header and non fouler trick very easy and you no longer have to worry about a CAT and it WILL pass emissions testing.(breakn)
Technically its the precat our cars have 2 cats, precat to help untill the primary is warmed up to help with cold start emissions after its warmed up its just power loss.not trying to be smug about it or a dick just for clarity so nobody gets confused. But 9 times out of 10 p0421 is the precat bad my down stream o2 sensor threw its own code but just to be on the safe side is there a proper way to test it other than just looking at it to see if its white? Of course after I fixed it I got the p0421 but I used the non fouler and deal with a stinky car
