Utahkompressor

I googled P0420, then came across a subaru forum and saw how they solve the P0420 issue with Spark Plug Non-Foulers. Basically, they just pull the post-cat sensor out of the exhaust stream which trick the computer into thinking that the cat efficiency is okay. I'm tired of erasing P0420 every week, so I decided to give it a try. Plus, it only costs a few bucks...won't hurt if it doesn't work.

All you need is a Dorman 42002 Spark Plug Non-Foulers. Drill a half inch hole on one of them then screw them together...the big hole on top and small hole on the bottom. Put a little bit of anti-seize on the threads then install them between the post-cat port and the sensor. Done!

I've had them on for over a month now, and so far so good. No CEL, no pending code. I attached the comparison charts for you to see, it definitely lower the voltage reading from the post-cat sensor.

jetta02awp

This is what I used when I had my Jetta and a high flow cat.
http://store.42draftdesigns.com/O2-S...cer_p_306.html

Worked fantastic. It basically does the exact same thing, moves the sensor out of the exhaust stream

phister

you instead of drilling the holes most buy the 42002 and screw into the 42009

phister

i bought might mine from corsport for my EP3 because i needed an angled one

http://www.corsportusa.com/store/cat...words=defouler

Utahkompressor

Yeah...I looked at the angled one too. They probably work better, but way too expensive. I'm cheap-***, so a pack of 42002 works for me!