so i got this code P0421
 

So i just got myself a 03 lancer and sadly i already got my first CEL[:'(]
the code im getting is this P0421 Warm Up Catalyst Efficiency Below Threshold (Bank 1)

since i dont know a thing about my lancer yet, i wanted to see if the experienced guys in this forum can help me out :D

any suggestions would be gladly appreciated!

RE: so i got this code P0421
 

Catalytic converter is out. Either that or an o2 sensor. 100% positive its one of those. Im betting on the cat.

RE: so i got this code P0421
 

yep. the cat is out. fairly common on the lancers how many miles do you have on the car? there is some kind of a warranty extension for certain cars that are having this problem. i just replaced one on an 03 lancer

RE: so i got this code P0421
 

..go down a couple of threads.

look at the replys to "my baby's sick".

RE: so i got this code P0421
 

checked it out, thanks!



so what would you guys recommend?

an oem cat,a test pipe,or any other suggestion?

oh and is it bad driving around with my cat messed up?

RE: so i got this code P0421
 

95k

so what cat do you recommend?

RE: so i got this code P0421
 

dude i have the same problem but different people keep telling me different things like its DEFINITELY the header....im starting to believe that its the header that is out cause of the many people with the same problem....ima get a new header tomorrow and ill let you know what that does

RE: so i got this code P0421
 

yea for sure keep me updated!

RE: so i got this code P0421
 

there should be 2 sensors on your car one in the header and one near the Catalyctic Converter the same with the 2008 Lancer.

Road Race is developing the Headers for the PZEV engine. for now they're only selling the non pzev engine- Headers

RE: so i got this code P0421
 

@ 95k you're past the warranty extension if your car was even a part of it. i wouldnt recommend test pipecuz you're check engine light is still gonna be on