My wife's car recently had the SES light come on. Of course, it's the dreaded P0421 code. Of course, our car has over 100K. Of course, she's do for smog in March.

I've searched the forum for 3 days now and my questions are...If I successfully remove the SES light via the spark plug non-fouler fix, would I be able to pass the tailpipe smog test here in CA? Would Seafoam help any? Would running premium fuel help?

Currently, our funds are too low to fix the cat. Any help would be appreciated. Thank you.

 

what kind of car?

 

and description of the code?

 

if its for a lancer check for loose connections on the o2 sensors, check for crack in the exaust header as one user found out here https://www.evolutionm.net/forums/la...hreshhold.html

https://www.evolutionm.net/forums/la...-anything.html

from what i understand it points to a bad cat, hard not to miss when u look underneath.... i read theirs a recal for the cat for the lancer..

might wanna call the dealer to see about the recal for the cat conv

 

I passed on Sunday! The car was a 03 Lancer ES and it has 115K miles. I called Mitsu and they aid there were no recalls open for my vehicle and it didnt matter anyways beacause of my mileage. I ended up buying an Autel MS300 code reader from amazon for $30. I used it to erase the SES light and also was able to tell when my computer was emissions "ready". Once it was ready, I took it in. I don't know if it helped but I also ran 91 fuel.