CEL p0301

Discussion in 'Gen 4 Prius Technical Discussion' started by amos, May 4, 2021.

  1. amos

    amos Active Member

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    hello all
    my 2016 has just over 150k miles on it, owned for 2 years. yesterday was the firt time i got this cel p0301. my obd says "cylinder 1 had too many misfires within a predetermined period of time".
    i last replaced all spark plugs 60k miles ago (2 yrs) with denso sc16hr11. those guys at autozone today recomended replacing the coil for a cost of 95$ each but i didnt take their advise yet.
    car started hasitating when accelerating and i had those bad thoughts about what went wrong. it seemd like all hybrid was functioning right, vibration kicked in soon as i accelerated and gas engine was on .. when driving a steady speed on the freeway , all was good but had to go down on the speed to 45mph, was hard to get accelaration without those vibrations.
    bought 4 spark plugs and only replaced that one just to see if anything.
    well cel is still there but seems like car driving ok again. i didnt want to erase it , waiting to see if will go by itself.
    this the old one.
    IMG_20210504_154237[1].jpg IMG_20210504_154704[1].jpg
     
  2. bisco

    bisco cookie crumbler

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    doesn't look bad, but the gap seems large?
     
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  3. alanclarkeau

    alanclarkeau Senior Member

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    Yes, does look large in the photo - wondering if the "don't adjust the gap" on this type plug still is current?
     
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  4. amos

    amos Active Member

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    new plug has a more sharp end of the tip.
    car drives fine, i wonder if ignition coil needs to be replaced, i know its not really common for this item to fail
     
  5. priusgreymint

    priusgreymint Member

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    Couple recommendations:

    1 . buy one new spark plug see if it solve the problem

    2. remove the coil from different cylinder and
    See if the CEL follows the coil pack?

    3. I know that Gen 3 Prius have head gasket issue. Usually on gen 3 a mis fire on cylinder one is due to head gasket failure. I don’t know if gen 4 has the same issue maybe someone knowledgeable in gen 4 can advice. There are kits you can buy to see if coolant line mixture.
    Do you hear the knock during cold start? I would keep an eye on your coolant level? If your loosing coolant there is leak usually head gasket.

    good luck keep us updated on your root cause.
     
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  6. Mendel Leisk

    Mendel Leisk Senior Member

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    Just swap them around and see if the code moves.
     
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  7. amos

    amos Active Member

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    mmm good idea , will do tomorow
     
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  8. amos

    amos Active Member

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    so far it seems like a failed plug, no similarity at all to the gen 3 symptoms, car is driving good after i changed only one plug of cylinder#1, i will swap those coils as @Mendel Leisk suggested and see.
    denso plugs i had were supposed to hold 100k. that faulty one lasted only 60k, i now have autolite there so lets see.
     
    #8 amos, May 10, 2021
    Last edited: May 10, 2021
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  9. priusgreymint

    priusgreymint Member

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    Keep us updated and monitor coolant level
    But it could be a slow leak. Might be head gasket issue.
     
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  10. TMR-JWAP

    TMR-JWAP Senior Member

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    I'm pretty sure the SC16HR11 is supposed to be a fine wire iridium type plug and should last 100k+ miles. The plug in your photo is no longer a fine wire plug, as it's completely burned away, leaving a huge gap. This is very typical of Chinese counterfeit plugs. If so, you're lucky to have gotten 60k miles from them. Where were they purchased?

    I wouldn't waste any time. Replace the rest of them also.
     
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  11. Mendel Leisk

    Mendel Leisk Senior Member

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    Another pic would help; OP pic focused on paper in background.
     
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  12. amos

    amos Active Member

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    Well so far theres no coolant missing and engine oil didnt drop. I have already 8000miles since last change. Not a drop of oil missing. What kind of leak? Only thing rhat worries me is that faulty plug i took out had signs of rust like color ( yellow orange). Last time i fueled was sinclair station im thinking maybe that gas had some water in it. That was the only place that sold gas under $4/gal. but now that all is gone, seems like counterfit denso plugs bought at ebay.
     
    #12 amos, May 12, 2021
    Last edited: May 12, 2021
  13. amos

    amos Active Member

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    thats the only pic i took with the obd reading. i decided to reset the code cause it didnt go by itself, didnt swap the coils, code not showing anymore
    IMG_20210510_121303_481[1].jpg
     
  14. amos

    amos Active Member

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    purchased it at ebay, was $24 for the set x4 on may/06/2019
    this seller is not at ebay anymore, could be a chinese counterfit,
     
    #14 amos, May 12, 2021
    Last edited: May 12, 2021
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  15. amos

    amos Active Member

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    update
    at first i have only changed the 4 spark plugs and reset the fault code p0301.
    been a month and about 2500-3000 miles
    2 weeks after the reset, CEL is back, i was accelerating up from 70 mph on fwy, first it was flashing and than became permanent, went home and reset the same code again p0301. this time i have also swapped ignition coil of cyl1 with cyl2, (to see if i will get a p0302 ).
    yesterday again, i was accelerating on fwy uphill from 70mph to about 80mph, CEL started flashing so i've let go off the gas pedal and slowed down, an hour driving same ride engine is still on and again on fwy i accelerated hard and CEL started flashing, again i let go the gas pedal, CEL is off.
    this morning i checked with OBD, no reording of any code.
     
    #15 amos, Jun 8, 2021
    Last edited: Jun 8, 2021
  16. TMR-JWAP

    TMR-JWAP Senior Member

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    A flashing CEL is caused ONLY by a serious misfire.

    Misfires are caused not only by bad sparkplugs or coils, but also fuel injectors, wiring or anything that messes with the fuel/air/spark cycle.
     
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  17. amos

    amos Active Member

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    I will try a red line SI-1 i know it has a high concentration of PEA.
    I thought if a flashing cel records a code. So far no codes recorded. I also visually checked the injector harnes .all seems fine. No broken wires or loose connectors issue.