Just passed 100k got my first check engine light

Discussion in 'Gen 4 Prius Care, Maintenance and Troubleshooting' started by PatricioDaSilva, Apr 16, 2022.

  1. PatricioDaSilva

    PatricioDaSilva New Member

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    My 2018 Prius just passed 100k and I got my first check engine light.

    I thought it might be the gas cap loose. Well, it was. Whew! I thought. However, I drove it a hundred miles and the check light didn't go out like I believe it was supposed to. Thing is, I noticed my gas mileage improved. I was getting 52mpg now I'm getting 57 ! What would explain that?

    Anyone experience this at 100k with your 4th gen prius ? What was wrong?

    Anyway, going to service it first thing Monday, and, by the way, the car runs perfectly, and always has. Changed the oil regularly rotated tires, every 5k etc. I haven't changed the HV Filter and maybe I should do that, and just take it in for a good overall inspection. I just found out I was supposed to change it every 10k. I hope I didn't damage anything.
     
    #1 PatricioDaSilva, Apr 16, 2022
  2. ChapmanF

    ChapmanF Senior Member

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    After the service visit, you can post here what diagnostic code(s) got read from the car, and then we can say more about why the light was on.

    Regrettably, we can't say very much just by knowing that the light was on, or even that the car runs perfectly or not.
     
    #2 ChapmanF, Apr 16, 2022
  3. PatricioDaSilva

    PatricioDaSilva New Member

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    I got the PO300 code. Misfiring. I'm having new plugs and coils put in.
     
    #3 PatricioDaSilva, Apr 17, 2022
  4. bisco

    bisco cookie crumbler

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    that doesn't bode well...
     
    #4 bisco, Apr 17, 2022
  5. BiomedO1

    BiomedO1 Active Member

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    Shotgun approach - NICE.... I believe the spark plugs are at or near the end of their service interval. Ask for your old parts back. You can look at the spark plugs to see how each cylinder is burning - though you won't know which plug came from which cylinder. It'll give you a clue to what to go after next if this doesn't solve your P0300 issue. It would be nice, if you just burned the tips off of your spark plugs; that way you know definitively that you solved the misfire.

    IMHO: Get the ATF changed, if that hasn't already been done. It's cheap insurance, if your planning on keeping the car. Has the EGR been cleaned out.
     
    #5 BiomedO1, Apr 17, 2022
    Last edited: Apr 17, 2022
  6. Rmay635703

    Rmay635703 Senior Member

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    If the evap (or other fuel system components) have a problem it can make the computer show you as getting better MPGs but it’s only a fictional number on the computer while in reality your MPGs actually are lower,
     
    #6 Rmay635703, Apr 17, 2022
  7. Jburner

    Jburner New Member

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    Is EGR clogging up even an issue on the 4th gen? I thought it was a redesign and not as susceptible to the 2nd and 3rd gen EGR issue.
     
    #7 Jburner, May 13, 2022 at 11:45 PM
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