Catalytic converter question P0420

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by JC91006, Oct 26, 2015.

  1. JC91006

    JC91006 Senior Member

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    Need some help from people that know about Catalytic converters. My check engine light has been coming on and off and it seems to show P0420 for catalytic converter. The light stays off for about a week and it'll come on for a day or two and off again.

    Wouldn't a failed converter stay failed? Can P0420 be triggered by loose/bad gas caps?
     
    #1 JC91006, Oct 26, 2015
  2. johnnyb588

    johnnyb588 Member

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    P0420 can go on and off intermittently. It did that on my 1999 Tacoma. P0420 means failing, not necessarily failed 100%.

    If you're throwing a P0420, I think the cat needs to be replaced before you ruin your O2 sensors.

    FYI, if you had a bad downstream O2 sensor, I'm pretty certain that would throw a different code, but it might be worth checking the functionality of that sensor before you replace the cat. And lastly, OEM is the way to go for a cat, imo.
     
    #2 johnnyb588, Oct 26, 2015
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  3. JC91006

    JC91006 Senior Member

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    I can't believe this just happened after getting a new replacment HV battery. If it failed a month earlier, it would've been free. I was able to find another part off another wrecked 2005 car, but since that one is original and has 200k miles, I didn't think it would last long....so I passed on it.
     
    #3 JC91006, Oct 26, 2015
  4. johnnyb588

    johnnyb588 Member

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    Also, I'm not a mechanic, but a lot of weekend warriors on the internet swear than things like MAF cleanings, PCV cleanings, and new upstream O2 (or A/F) sensors can help with P0420's. If things are cheap/free, it might be worth looking into those options if you have the time. Chances are, however, that it's just a bad cat, unfortunately.
     
    #4 johnnyb588, Oct 26, 2015
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