Need advice on p420 code

Discussion in 'Prius v Main Forum' started by Blurredforlife, Jun 3, 2025 at 10:01 PM.

  1. Blurredforlife

    Blurredforlife Junior Member

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    Not sure if its my oxygen sensor or bad or clogged catalytic converter or both. I had a misfire a month ago. Obviously runs alittle rough on start. Once warm it runs fine. Any thoughts on pics I posted. Thanks
     

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  2. bisco

    bisco cookie crumbler

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  3. Blurredforlife

    Blurredforlife Junior Member

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    Is it one sensors or the catalytic converter..or both. Thanks
     
  4. Blurredforlife

    Blurredforlife Junior Member

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    I posted a few pics but I'm not sure. Pretty sure the upstream and down stream oxygen sensors are original. The vehicle has 235k. Actually have never had to replace a down stream oxygen sensor on any toyota I've ever owned.
     
  5. rjparker

    rjparker Tu Humilde Sirviente

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    Usually the sensors have their own codes. P0420 is most often a bad cat, typically caused by oil burning.

    You can check the vehicle's cat efficiency monitor which runs almost every drive cycle.

    Example from Car Scanner app on my v.
    IMG_8467.jpeg
    This is a particularly good reading. Most captures are closer to the minimum.

    Note the egr flow test above. That is a good result and will repeat closely each capture. That is with two cleanings in 325k miles and one updated egr valve.

    The following is a more detailed method to manually check the cat by analyzing the sensors
    IMG_8466.jpeg

    Finally if I get to the point where cat replacement is necessary (in a non Carb state)

    IMG_8468.jpeg

    Walker cat detail
     

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    #5 rjparker, Jun 4, 2025 at 2:45 PM
    Last edited: Jun 4, 2025 at 2:55 PM
    Brian1954 and Blurredforlife like this.
  6. Blurredforlife

    Blurredforlife Junior Member

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    Thanks so much for posting this. Much appreciated