06 prius 113k miles with dreaded p0420 code

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by DodgeTransmissionsGoBoom, Aug 30, 2021.

  1. DodgeTransmissionsGoBoom

    DodgeTransmissionsGoBoom Junior Member

    Joined:
    Aug 30, 2021
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    Location:
    NC
    Vehicle:
    2006 Prius
    Model:
    ----USA----
    I recently bought an 06 prius with what i thought just needed a HV battery but turned out to need a battery and inverter but a few days later i got those both replaced. Now i’ve been driving it and the CEL keeps coming on in less then 50 miles for p0420 cat inefficiently. Is it really possible for a cat to fail this early? i tried to look at post cat sensor data but it seems to hang around .8v if i remember correctly. when i bought it the gas was a year old in it and it barely made it to the gas station misfiring and struggling due to the low octane so i shot a few gallons of premium in it and the misfires went away and ran fine so i went for a drive and it popped up so i thought maybe it was just the old gas so i drove it until the last bar started blinking then filled it up with 93 and cleared the code and within 50 miles it popped back up again! Could i be lucky and just need a sensor or is the cat really dead at only 113k miles?
     
  2. JC91006

    JC91006 Senior Member

    Joined:
    Nov 10, 2013
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    Location:
    Los Angeles, CA
    Vehicle:
    2008 Prius
    Model:
    II
    That catalytic converter is worth $1000 so if you change it out, don't discard it. Also be very careful not to park this car on the streets, that valuable catalytic converter will vanish by morning.

    If you want to throw a part at it, you can buy a Denso downstream oxygen sensor from Amazon for $42.00. That may fix the problem.
     
  3. Damien1337

    Damien1337 New Member

    Joined:
    May 12, 2022
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    Location:
    California
    Vehicle:
    2005 Prius
    Model:
    Five

    How did this end up working out for you? I'm having a similar issue at 140k miles.
     
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