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P0420 Connundrum PLEASE HELP

Discussion in '3rd Gen 4Runners (1996-2002)' started by mogie, Mar 6, 2020.

  1. Mar 6, 2020 at 10:58 AM
    #1
    mogie

    mogie [OP] New Member

    Joined:
    Feb 26, 2020
    Member:
    #13297
    Messages:
    10
    Gender:
    Female
    First Name:
    Caitlin
    Northern California
    Vehicle:
    1998 4Runner 3.4L V6...430,000 miles and counting
    I'm in CA and I was supposed to get my bi-annual smog in Dec. of 2018. The P0420 code has prevented me from doing so. I have a 1998 4wd manual with 380,500 miles.

    -Has passed all previous smogs since I purchased it in 2010 (2010, 2011, 2012, 2014, 2016)
    I got it smogged in March 2019 after turning the CEL off praying that somehow it might pass. PASS on emissions, FAIL on functional check (due to CEL)

    -New CAT in 2012 (roughly 130,000 miles ago)
    Old CAT was stolen
    No rotten egg smell, isn't excessively hot, no loss of power

    -Replaced o2 sensors (twice)
    Haven't replaced them with Denso but could this really be my problem?

    -Repaired exhaust leaks

    My exhaust (tailpipe) broke off at the back of the muffler. Would that be an issue even though it's after the cat and sensors?

    Any advice is much appreciated! I love my truck and it runs great despite it's age and mileage, I would like to keep it on the road!
     
  2. Mar 6, 2020 at 1:04 PM
    #2
    4x Old Guy

    4x Old Guy New Member

    Joined:
    Aug 2, 2019
    Member:
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    Messages:
    280
    Gender:
    Male
    Riverside, CA
    Vehicle:
    2019 Silver TRD Off-road Premium
    Big-O Bigfoot A/T tires
    I have a 2003 Tacoma. Broke down and replaced the O2 sensor with the $$ Denso one. When it comes to smog sensors, OEM parts are best. Also, check the wiring (a longshot, but possible). Loose or corroded connectors or damaged wire can give the computer faulty info.

    https://www.autocodes.com/p0420_toyota.html
     
  3. Mar 6, 2020 at 7:25 PM
    #3
    mogie

    mogie [OP] New Member

    Joined:
    Feb 26, 2020
    Member:
    #13297
    Messages:
    10
    Gender:
    Female
    First Name:
    Caitlin
    Northern California
    Vehicle:
    1998 4Runner 3.4L V6...430,000 miles and counting
    Thanks 4x! I've had conflicting advice on whether or not to go with the Denso's but I think I'm going to buy the sensors now. It's better than taking it to a mechanic and spending hundreds of dollars just to have them replace something I can already do myself!
     
  4. Mar 12, 2020 at 8:05 AM
    #4
    negusm

    negusm New Member

    Joined:
    Oct 22, 2019
    Member:
    #11745
    Messages:
    1,876
    Gender:
    Male
    Vehicle:
    2002 4Runner SR5 4WD
    Anyone says that OEM parts are not as good, or your wasting your $$, they don't know TOYOTAs. Mile for mile, TOYOTA parts are ALWAYS cheaper, hands down.
     
  5. Mar 12, 2020 at 8:54 AM
    #5
    4x Old Guy

    4x Old Guy New Member

    Joined:
    Aug 2, 2019
    Member:
    #10764
    Messages:
    280
    Gender:
    Male
    Riverside, CA
    Vehicle:
    2019 Silver TRD Off-road Premium
    Big-O Bigfoot A/T tires
    Denso manufactures OEM parts for Toyota (like Delco does for GM and Autolite does for Ford). You can get the “Toyota” part from the dealer for $$$, or get the Denso part from a “real” auto parts store (that supplies professional auto repair shops, not DIY places like Autozone or O’Reilly, etc) for $$.
     
  6. Mar 12, 2020 at 9:14 AM
    #6
    negusm

    negusm New Member

    Joined:
    Oct 22, 2019
    Member:
    #11745
    Messages:
    1,876
    Gender:
    Male
    Vehicle:
    2002 4Runner SR5 4WD
    Correct. I should have been clearer. I know TOYOTA doesn't make their parts. Just like the AISIN water pumps are the same as what TOYOTA uses, etc.
     

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