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Faults PO420 (catalyst system efficiency below threshold) .

Discussion in 'Gen 3 Prius Main Forum' started by dgm1214, Sep 15, 2024 at 6:34 PM.

  1. dgm1214

    dgm1214 Junior Member

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    This popped up after replacing both oxygen sensors, on a 2013 with 177k miles. Prior error was related to faulty downstream oxygen sensor, and found wires from connector damaged. Did this work myself with sensors off Amazon, about $40 each.
    Wondering if I did something wrong ?
    Thanks !
     
    #1 dgm1214, Sep 15, 2024 at 6:34 PM
  2. dgm1214

    dgm1214 Junior Member

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    Update, reset codes again, and after 50 miles NO codes popped up. Will test drive tomorrow too.
     
    #2 dgm1214, Sep 15, 2024 at 9:25 PM
    bisco likes this.
  3. bisco

    bisco cookie crumbler

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    good luck!
     
    #3 bisco, Sep 16, 2024 at 2:09 PM
  4. dgm1214

    dgm1214 Junior Member

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    Update2. Drove only about 5 miles today before engine light appeared. Same 2 codes as before

    1) P0420 catalyst system efficiency below threshold Bank 1
    2) vehicle has no faults

    wondering why it says ‘no faults’ when it reported a P0420.
    Not sure if I should drive it on a trip, 700 miles one way into Canada, or not.
    Thanks for suggestions.
     
    #4 dgm1214, Sep 16, 2024 at 3:16 PM
    Last edited by a moderator: Sep 16, 2024 at 4:09 PM
  5. bisco

    bisco cookie crumbler

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    were the new sensors oem?
     
    #5 bisco, Sep 16, 2024 at 8:15 PM
  6. MAX2

    MAX2 Member

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    How did you read the errors from the machine? Program? Scanner?

    The error of low efficiency of the catalyst is most often critical for the environment and sensitive sense of smell.
    The exhaust pipe smells like donkey urine.
    The car continues to drive without any problems.
     
    #6 MAX2, Sep 17, 2024 at 12:24 AM
  7. AzusaPrius

    AzusaPrius Senior Member

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    Try a bottle of Cataclean that stuff works.

    Also using your car while this code is on is not good for the ICE as it can cause back pressure and ruin your engine.

    If it is original OEM cat then it is time and most likely it is bad as they do not last more than 7-10 years.
     
    #7 AzusaPrius, Sep 17, 2024 at 12:29 AM
  8. Eddie25

    Eddie25 Active Member

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    You generally never want to get important engine management parts like o2 sensors from Amazon.

    I'd be skeptical that the original code was for sure related to a faulty downstream sensor. What code, and how did you come to that conclusion? Could it have JUST been the damaged connector? If feasible, put the old sensors back in with a repaired connector and see what happens.
     
    #8 Eddie25, Sep 17, 2024 at 10:40 AM
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