P0301. Replaced coil & spark plug, now it's returned.

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by SicilianDragon, May 1, 2021.

  1. SicilianDragon

    SicilianDragon New Member

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    Just hoping I can get some theories on the most probable causes here.

    My Check-Engine light came on with the P0301 code.

    I got a new spark plug and ignition coil, and had them both replaced. For about a month and a full 1000 miles, the light stayed off. Also, it ran perfectly--not a trace of shaking or anything.

    Now suddenly the light is back on again; exact same code: P0301. What is the most probable cause here? I know that paying someone just to look at it is the only way to know for sure, but mechanics have given the runaround when I've asked. They say things like "I guess it's not the spark plug/ignition coil," but they're glossing over what I said above ("For about a month and a full 1000 miles, the light stayed off. Also, it ran perfectly--not a trace of shaking or anything") -- if it had nothing to do with those parts, why would replacing them have solved it temporarily?

    I know sometimes generic brands aren't the best, and I'm planning to replace them again with higher-quality parts. But I don't want to do this and have it revert back in another month.

    Any theories? Thanks for any help.
     
  2. Tideland Prius

    Tideland Prius Moderator of the North
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    Do you have a regular Prius or a Prius v?
     
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  3. Air_Boss

    Air_Boss Senior Member

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    Plug fouling due to…
     
  4. SicilianDragon

    SicilianDragon New Member

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    You're right, I posted in the wrong section. The labeling has confused me nonstop from the beginning. It's a regular 2013 Prius...the grade is Four. Is that the same as 4th generation?
     
  5. rjparker

    rjparker Senior Member

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    Possible head gasket. Intermittent and initially self sealing is its MO.
     
  6. ChapmanF

    ChapmanF Senior Member

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    How many miles on the car?

    The usual recipe for troubleshooting a misfire hasn't changed from the olden days. Check compression, check fuel mixture, check spark.

    Sounds like you've checked the spark part. Where did you get the plug and igniter? An investigation conducted in Australia found sixty percent of spark plugs purchased online to be counterfeit. (I haven't found a report on what the corresponding figure is closer to home.)
     
  7. Mendel Leisk

    Mendel Leisk Senior Member

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    ^ @SicilianDragon please provide this. Also, how’s the coolant level in the engine reservoir?
     
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  8. SicilianDragon

    SicilianDragon New Member

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    Just over 190K miles.

    The plug and coil were purchased at a well-known and publicly trusted discount auto parts shop, in person. Of course Toyota would recommend their specific factory-made parts, but that's also to put more money in their pockets.

    Don't have an up-to-date answer on the coolant level, but I will provide this ASAP. I know it has never overheated...but conversely, the air has pretty much stopped blowing, so this could be related.

    I will make note of the procedure suggested:
    • Check compression,
    • Check fuel mixture,
    • Check spark.
    Is there somewhere I could find out the basics...or could you add a few more words to these phrases so someone as mechanically ignorant as myself can comprehend the basics of what this means (ie. what aspects of these things need to be checked)?

    If it's a head gasket, I'm dead and buried. That's what happened to the 2000 Civic I had before this, and I had to junk it. But this one still has payments to go, and I couldn't afford the head gasket repair--yet the vehicle is a necessity for my income (UberEats, GrubHub, etc.)

    Thanks everyone for all the help so far.
     
  9. Tideland Prius

    Tideland Prius Moderator of the North
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    2013 is a 3rd generation (2010-2015). I've moved it this thread for you.
     
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  10. SicilianDragon

    SicilianDragon New Member

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    UPDATE: I topped off the coolant, but it was never very low in the engine unit or the power control unit--closer to "full" than "low."
     
    #10 SicilianDragon, May 2, 2021
    Last edited: May 2, 2021
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  11. Tim Jones

    Tim Jones Active Member

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    It should never be low........
    Never had to add any until Head Gasket Failure.
     
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  12. Mendel Leisk

    Mendel Leisk Senior Member

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    With those miles the Exhaust Gas Recirculation components, and the EGR passages in the intake manifold, will likely be WELL along in the clogging-with-carbon process.

    I wouldn’t t delay; clean-out is past due. I’m one of the “addled believers”, that carbon-clogged is not “situation normal”, and can lead to head gasket failure and all that can ensue.

    More info on cleaning here:

    Bad Flywheel | PriusChat

    P0301 technically means misfire on cylinder one (passenger end cylinder). With the Exhaust Gas Recirculation passage at cyl 1 port regularly being the first to fully clog, and the head gaskets regularly failing at cyl 1, a leak-down test should maybe be step. It can confirm head gasket integrity, and if it’s leaking, where. Then go from there: EGR cleaning, HG replacement followed by EGR cleaning, engine swap, or just sell/trade.
     
    #12 Mendel Leisk, May 3, 2021
    Last edited: May 3, 2021
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  13. Tim Jones

    Tim Jones Active Member

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    You know it's clogged. Wonder if this could be egr stuck.
     
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  14. Tim Jones

    Tim Jones Active Member

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    My v in Toyota for brake system. They gave me a RAV 4.
    It's ok but I like the Mazda I rented while out of town. Don't know the name but really nice suv. Excellent backup camera system.
     
  15. SicilianDragon

    SicilianDragon New Member

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    Well...maybe that's some hope that this isn't a head gasket failure...

    Same thing happened to my Civic when the head gasket blew. Had to keep pouring coolant after every trip.
     
  16. Mendel Leisk

    Mendel Leisk Senior Member

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    Maybe CX5? That’s mid of their CX3/5/9 range. Our son’s got one, likes it.
     
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  17. SicilianDragon

    SicilianDragon New Member

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    That reminds me...my camera now only works about half the time. That applies to the screen in general, whether showing the reversal view or the selection screen. Sometimes it's fuzzy and invisible, sometimes normal. That's a different issue though--on top of the air not blowing anymore.
     
  18. Tim Jones

    Tim Jones Active Member

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    Lot's of other stuff will be going bad fairly soon.....
     
  19. SFO

    SFO Senior Member

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    There are some local LA shops that were offering HG replacements in 1100+ range (pre normal), don't have the links handy, but will check.

    Try "gasket masters" in Modesto, unknown if they charge extra for travel time down to LA. Unsure what the current rate is, but it was around 1k with a new water pump a couple of years ago. Please update with your findings. Here is one of their postings for Fresno, not that far of a drive. PRIUS PROS-GASKET MASTERS HEAD GASKET REPLACEMENT ON SITE -...

    From the posting above, it looks like the 'dynamic duo' has added a new young man to the crew. Their newer YT video claims to be serving multiple cities in various western states. The job takes them about 2 hours total.

     
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  20. Tim Jones

    Tim Jones Active Member

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    I have done this and it's pretty hard especially without professional tools.... But I do have a backup vehicle and was able to take my time.
    This shouldn't be happening to so many cars..... Toyota dropped the ball big time on this...
     
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