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P420 error after CAT/O2 replacement - best fix?

Discussion in 'Gen 2 Prius Technical Discussion' started by NMJack42, Mar 24, 2022.

  1. NMJack42

    NMJack42 New Member

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    2007 Prius 100k - Catalytic Converter was stolen and replaced with non-OEM CAT six weeks ago. the O2 sensor was also replaced. P420 code came up yesterday. The car does not burn oil...yet

    What's the best fix for this?
    1) replace O2 sensor with a OEM Denso sensor
    2) use a "cheater"/extension/bung on the O2 sensor - part number?

    any other ideas?
     
    #1 NMJack42, Mar 24, 2022
  2. SFO

    SFO Senior Member

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    Are the local smog techs looking for OBD2 codes reported, or will they check under the car and down the firewall as well?
     
    #2 SFO, Mar 25, 2022
  3. NMJack42

    NMJack42 New Member

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    I'm in Illinois - Emission testing in this state is a joke - they only check if you have any OBD2 codes. They do not check under the car or inspect the CAT.

    (i think that's what you're asking).
     
    #3 NMJack42, Mar 25, 2022
  4. audiodave

    audiodave Active Member

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    Get a cat that works.
    Magnaflo is the brand I used in California. It was illegal at the time but place I test at just looks for codes. It's passed 3 times with no codes.

    Posted via the PriusChat mobile app.
     
    #4 audiodave, Mar 25, 2022
  5. vvillovv

    vvillovv Senior Member

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    #5 vvillovv, Mar 25, 2022
    Last edited: Mar 25, 2022
    audiodave likes this.
  6. SFO

    SFO Senior Member

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    If DIY then trying the extender would be the cheaper option, though I've never used one myself.

    If that doesn't work, you could try the denso o2 sensor for 50 or less (Carid will pricematch any retailer) : More Information for DENSO 2344623

    Is the current installation leak free?

    Is the vehicles mileage accurate?

    Which non-oem cat did you use, and do you have access to techstream?
     
    #6 SFO, Mar 26, 2022
  7. NMJack42

    NMJack42 New Member

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    Update - the check engine light just went away. It solved itself. I'll pray it doesn't come back.
     
    #7 NMJack42, Mar 27, 2022
    audiodave likes this.
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