P0420, only in the rain
+ Reply to Thread
Results 1 to 3 of 3

This is a discussion on P0420, only in the rain within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; So, my car's been through a few entire I/M readiness cycles, and just twice the CEL has come on with ...

  1. #1
    Registered User poly_poly-man's Avatar
    Join Date
    Feb 2010
    Rochester Institvte of Technorcery

    P0420, only in the rain

    So, my car's been through a few entire I/M readiness cycles, and just twice the CEL has come on with P0420. Both times it's been on a highway in the rain. I'm seriously thinking that the problem is not a cat problem, but an O2 sensor problem.

    I'd like some other opinions, though. What would cause an apparently good exhaust to say that there are cat efficiency problems in the rain?

    I took a look at the sensor itself (didn't take it out), and the wire seems loose but not broken I don't think... not sure how to tell if it's bad without replacing.

    Anything I can check, datalog, take pictures of, etc. to diagnose this problem? I'm probably going to do the mechanical CEL fix later on when I go nearly or totally catless, but I'd like to make sure that there's not a problem with the sensor or its wiring...

    Any ideas appreciated.
    My big thread: The Used WRX Buying Checklist - Please Contribute!

    My current car: 2002 WRB WRX Wagon.
    Mods: GM BCS, Carberry SD rom, uppipe, AEM UEGO, Klunk Killer, F+R shifter bushings, head unit

  2. Remove Advertisements

  3. #2
    Moderator Donkey's Avatar
    Join Date
    Apr 2005
    Da boonies,Va
    I Support ClubWRX
    Could just be an exposed connection at the wire. Maybe try using some liquid electrical tape or something where the wires go into the sensor.
    Resident Adviser @ WTF Tuning, LLC
    2002 FORESTER S
    1998 FORESTER S

  4. #3
    Super Moderator (Actually a SuperSpy) SD_GR's Avatar
    Join Date
    Jul 2002
    CA, US
    I Support ClubWRX
    Check the connection on both ends and the wire again. This is tough because you're not going to be able to fix something that works. I agree with Donkey.
    The world breaks everyone and afterward many are strong in the broken places. But those that will not break it kills. It kills the very good and the very gentle and the very brave impartially. If you are none of these you can be sure it will kill you too but there will be no special hurry. Ernest Hemingway, A Farewell to Arms, 1929
    WRX Info Links, Courtesy TheJ
    DISCLAIMER: Opinions expressed are the author's alone and are inherently worthless.

+ Reply to Thread

Quick Reply Quick Reply

Register Now

Please enter the name by which you would like to log-in and be known on this site.

Please enter a password for your user account. Note that passwords are case-sensitive.

Please enter a valid email address for yourself. We strongly suggest that you stay away from using aol, yahoo, msn, and hotmail accounts. Sometimes the mail server blocks the emails from our server. As a result you will not receive any notifications including the confirmation email.

Please select your insurance company (Optional)


Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.

Posting Permissions

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