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p0420, p0300, p0303

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Olscratch, Oct 16, 2017.

  1. Olscratch

    Olscratch Junior Member

    Joined:
    Jan 15, 2016
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    Location:
    Texas
    Vehicle:
    2010 Prius
    Model:
    II
    2010 Prius II at 189,000 miles just started throwing these 3 codes for catalytic converter malfunction and resulting misfire. She runs fine except at idle/low speeds if the batteries are low it will violently shudder/shake. Its burned a lot of oil since 120,000 miles. Since it started throwing these codes my friend and I have:

    Spark plugs have been changed (#3 was oily)
    EGR valve and Cooler have been cleaned (extremely caked)
    Intake manifold cleaned
    Throttle body cleaned
    PCV valve replaced
    Engine coolant was very low, replaced

    What should we attempt next? O2 sensors? Coils? Pay dealership to put on a new cat?
     
    #1 Olscratch, Oct 16, 2017
  2. fotomoto

    fotomoto Senior Member

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    Location:
    So. Texas
    Vehicle:
    Other Hybrid
    If you've been burning a lot of oil over the last 60,000 miles, I'd be suspect of anything downstream (sensors, cat). In Texas, you can get a much cheaper aftermarket cat (or used) and any muffler shop can install. Also, keep a closer eye on the coolant as there have been cases of blown head gaskets reported here.

    GOOD LUCK!
     
    #2 fotomoto, Oct 16, 2017
    Olscratch likes this.
  3. mjoo

    mjoo Senior Member

    Joined:
    Nov 9, 2016
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    Location:
    Michigan
    Vehicle:
    2010 Prius
    Model:
    III
    I'm afraid this sounds like a head gasket failure. Sorry

    Pixel XL ?
     
    #3 mjoo, Oct 16, 2017
  4. Olscratch

    Olscratch Junior Member

    Joined:
    Jan 15, 2016
    41
    15
    0
    Location:
    Texas
    Vehicle:
    2010 Prius
    Model:
    II
    Unable to let my beloved Prius go into that good night I decided to run a treatment of Pro grade Bar's Leaks Head Seal repair on it this weekend and miraculously it worked.

    #nodespairwithBar'sLeaksrepair
    #ifixedmycarbyusingBar
    #notdeadfromthathead
    #nocasketfromthisgasket

    I reset the codes and drove 100 miles after resurrecting it and it drove beautifully + the misfires never returned + not 1 drop of coolant lost.

    However the p0420 code did come back up, showing cat system under efficiency.
    Where should I start on that? Just try sensor replacement or go ahead get a new catalytic converter? Is it bolt on or welded?
     
    #4 Olscratch, May 14, 2018
    anonymous likes this.
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