Code P0420 catalist efficiensy below treshold
 

I have an 02 Spec-v and I Keep getting this code for some reason I Can't get rid of it. It can't be my precat cuse I don't have one, I have nismo headders. I changed my plugs, o2 sensor and cleaned the air filter. Could it be the MAF going bad? My car has 100k and I had the 90k service done on it. Any help would be really appreciated.

RE: Code P0420 catalist efficiensy below treshold
 

the code is poping up because your secondary o2 sensor isnt picking up any change from the precat and all obd2 cars throw that code when you remove the precat and put a header in place. the secondary 02sensor serves no purpose on performance only for emmissions. there is a way to confuse the ecu into thinking there is a pre cat by using an o2 sensor simulator. go to this website and this will fix your check engine light code p0450 http://o2simulator.com/. good luck

RE: Code P0420 catalist efficiensy below treshold
 

Cool, thanks man. That's what I thought but I just wanted to make sure. I'll give it a try and post the results ltr