Which O2 Sensor to go with-Error Code PO420
Results 1 to 4 of 4

This is a discussion on Which O2 Sensor to go with-Error Code PO420 within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; I have an '04 and recently came up with the PO420 engine code. Not sure if its the Cat or ...

  1. #1
    Registered User
    Join Date
    Dec 2004
    Posts
    14

    Which O2 Sensor to go with-Error Code PO420

    I have an '04 and recently came up with the PO420 engine code. Not sure if its the Cat or the post-cat O2 sensor. The car has no mods. Just wondering if there is a preference for O2 sensors, Bosch, NTK, Denso? I've cleared the code twice in a few days and it keeps coming back so i thought this would be first route to fix it. Any suggestions?

  2. Remove Advertisements
    ClubWRX.net
    Advertisements
     

  3. #2
    Moderator Donkey's Avatar
    Join Date
    Apr 2005
    Location
    Da boonies
    Posts
    6,083
    I Support ClubWRX
    Its the rear cat efficiency code. Denso or NTK is what I would use. Could also very well be a catalytic covertor issue.
    Resident Adviser @ WTF Tuning, LLC
    2002 FORESTER S
    1998 FORESTER S




  4. #3
    Registered User EvoEatr's Avatar
    Join Date
    Aug 2008
    Location
    Kennett Square, Pennsylvania
    Posts
    1,839
    Quote Originally Posted by Bengalswrx View Post
    I have an '04 and recently came up with the PO420 engine code. Not sure if its the Cat or the post-cat O2 sensor. The car has no mods. Just wondering if there is a preference for O2 sensors, Bosch, NTK, Denso? I've cleared the code twice in a few days and it keeps coming back so i thought this would be first route to fix it. Any suggestions?
    How many miles are on the vehicle? I have only seen a handful of rear o2 sensors go bad on well... any Subaru in general, what I can say from experience is 8/10 times its the cat. conv. Also most of the time the rear o2 goes bad it will throw a code for the sensor itself.

  5. #4
    Registered User
    Join Date
    Dec 2004
    Posts
    14
    There are 71K miles on the car. I am hoping that the Cat would be covered by the federal emission warranty of 8yr/80K, however the dealer will only do this if they replace the o2 sensor...which they are charging way too much. Denso or NTK, might have to try tha route first and see if a new sensor does the trick....
    Last edited by Bengalswrx; 11-11-2010 at 05:32 AM.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •