Hi all!

A buddy of mine has an 2002 OBW, auto, 2002 K miles on it. The dreaded P0420 code has appeared. It appeared about TWO years ago! Somehow he got it to pass inspection a year ago. He has replaced the front CAT, it seems to work fine, operating at correct temp. This is a few weeks ago. Code reappeared 30 miles fown the road after that. Then I suggest to replace the front 02 sensor , from the suggestion I got here. I also had this code, did the 02, it went away for me, got inspection! BUT this isn't working for him! He also has replaced the wires! And a few months back has done the Head Gaskets. The car runs fine!

 

ANY suggestions?????

 

 

THX, SubeeTed

There are several things that can cause the P0420 catalyst efficiency code to be generated, including simple things like exhaust system leaks. See http://www.catalyticconverter.org/news/news_page.cfm?Key=catalytic_converter-&News=120 for some ideas.

 

Was the replacement cat an OEM unit?

Since you said one front O2 sensor this must be an EJ25 and not an H6.

 

Someone on here recently posted that a pinched wire caused an O2 sensor code. It was recently after a headgasket job and the mechanics fixed it for free.

 

Leaks are said to be a cause (never seen it happen myself).

 

If the rear sensor can cause this I think i'd have a mind to replace it. If he's invested this much, sounds like he'd like to have it quite a bit more, I would just assume the rear O2 is eventually going to need replacing and do it now with everything else (front and cat already done).

By chance did you replace the O2 sensor with a generic type, whereby you splice wires new O2 wires onto the existing wiring of the original O2 sensor? If so, when I have done this, the wire splice never seems to last long, resulting in a new O2 code. Finally, I gave up on generic O2 sensors, and only install a sensor specifically made for that model car. No more splicing, no more sensor trouble.

The 02 sensor that was used was a Denso, OEM.

THX ALL!!!

Let us know how you make out. I have an 02 OBW with the same Front O2 sensor Bank 1 Code that didn't go away with 2 new O2 sensors (H6 with two sensors).

Hi ALL!

CEL is OFF now! My buddy has NEW sticker!

 

What it finally was, is to REPLACE the almost 2 year old CAts (from Subaru) that he put in BEFORE the Head Gaskets blew! His mechanic talked to his Subee connections about the on going CEL and code. It seems that when the HG blew, it contaminated those CATS, and throwing the P0420 code. And of course SUBEE wouldn't honor the warranty because of the SUBEE HG blow up!

THX ALL!

SubeeTed

I think I had the same code, it turned out be corrosion on the coil pack heads. Some sandpaper and a little break cleaner later and the code went away.