I am running a megan test pipe with STM extended o2 spacer. I haven't had any problems with the p0420 code being thrown other than every 10k miles or so. Well now I am getting the code every 100-300 miles or so.

What would cause it to be thrown all of a sudden so often? I have about 100k miles on my evo and I'm thinking maybe it's time to change the 2nd o2 sensor. Would that cause the code to be thrown?

I know the code is because it is seeing the same exhaust gasses as the 1st o2 sensor but why all of sudden now it's throwing it more often. I checked the o2 and spacer and everything is on there correctly.

Maybe I should try an angled defouler?

Thanks

 

did you clear the code?

go pick up another extender at autozone the HELP! item. i forgot the size but if u search on here you will find it. try adding another piece to extend it a little further.

 

I cleared the code but it starts coming back every 100-300 miles. Ill try another extender and see if if it works.

Thanks