P0300, P0301, P0302

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by priusG322, Sep 17, 2020.

  1. priusG322

    priusG322 New Member

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    Location:
    Dallas, Texas
    Vehicle:
    2012 Prius
    Model:
    Three
    Hey guys having some problems with my 2012 Prius three with 217k miles. This car has been nearly bullet proof for the 100k miles i've owned it. But this morning on a cold startup i heard a loud knocking/Shaking from the engine. The noise and shaking went away after about 30 seconds of idling. I Scanned the computer and got those codes in the title. A bunch of misfires. Oh and the check engine light never came on. When i brought it to the mechanic they scanned it and there were no codes. And they could not replicate the knocking noise either. They recommended replacing the spark plugs as they are likely way overdue. Any advice? Why didn't the check engine light come on? And why were the codes gone when they scanned it? Thanks in advance.
     
  2. bisco

    bisco cookie crumbler

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    what are you and your mech using to scan?

    why is basic maintenance overdue?
     
  3. fotomoto

    fotomoto Senior Member

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    Hopefully it's the spark plugs or COPS but considering your mileage and generation you should strongly look into a head gasket failure; check the coolant levels and also the oil for any discoloration.

    GOOD LUCK!
     
  4. fotomoto

    fotomoto Senior Member

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    OK, with some luck, it's just the (rare) cold start issue. Did you previously move it (or turn it on) and the cold ICE ran just for a few seconds before turning it off?
     
    jerrymildred likes this.
  5. Grit

    Grit Senior Member

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    With that many miles, I’ll get a leak down test of the gasket before chucking new parts at it. If the gasket is blown, no matter which parts you replace, you’ll get the shakes.
     
    #5 Grit, Sep 18, 2020
    Last edited: Sep 18, 2020
  6. priusG322

    priusG322 New Member

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    Location:
    Dallas, Texas
    Vehicle:
    2012 Prius
    Model:
    Three
    Hey thanks guys i went ahead and replaced the spark plugs and the ignition coils on the cylinders that were misfiring. I noticed the acceleration was much better and the car seemed to drive smoother. They checked the oil and it all seemed good. I really hope it isn't the head gasket tho i will look into it. I do remember right before it happened it was raining pretty hard while i was getting gas it may have been possible that moisture got into the tank and caused a misfire. Anyway thanks again fingers crossed.
     
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