Engine behaving strangely and check engine light on

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by anonymous, Feb 10, 2017.

  1. anonymous

    anonymous Member

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    Few days ago we got back from a ~580 mile trip and after that I noticed the engine acting strangely. Kinda hard to explain but it tends to run strangely and when it's not supposed to, for example, sometimes when stopping the engine spins up to a high rpm and then slowly slows down, and sometimes when crawling at low speed the engine spins up and down and up and down repeatedly. Basically it's like the engine is sick and stubborn and runs oddly when it's not supposed to and doesn't like to cooperate.
    Then yesterday the check engine light went on :eek:
    So… what could it be, and how critical is it, and what should be done?
     
    #1 anonymous, Feb 10, 2017
  2. Sam Spade

    Sam Spade Senior Member

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    First get it scanned for codes.
    That can be a symptom of a LOT of things.
    12 V battery going bad or connections loose.
    HV battery going bad.
    A bad batch of gas.

    Any warning lights come on ??
     
    #2 Sam Spade, Feb 10, 2017
  3. anonymous

    anonymous Member

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    We're going to go to an auto .parts. store and have them get the error code.
    No indications other than the check engine light and the engine's sound.

    My guess is a bad sensor somewhere providing bad data causing the system to improperly control the engine. Sometimes engine behaves normally, sometime engine behaves strangely.
     
    #3 anonymous, Feb 10, 2017
    Last edited: Feb 10, 2017
  4. Sam Spade

    Sam Spade Senior Member

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    Keep in mind that the scanners they use at an auto parts store might not read ALL of the codes from a hybrid. And the store might not have a list of those codes that are specific to your model.

    They should be able to give you a rough idea of what MIGHT be going on........but maybe not.
    They should be able to test the 12 V battery though.
     
    #4 Sam Spade, Feb 11, 2017
  5. Robert Holt

    Robert Holt Senior Member

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    Are you (or a designated passenger) watching the hybrid system display as this odd behavior is occurring? In particular, I think you might like to check the battery charge icon that has like eight lit bars it to see if it is associated with the HV battery going down to 2 bars, at which point the computer will switch on the engine to recharge the HV battery. I use a Scangauge to track engine rpm directly which would help clarify matters, but I'll assume you do not have that available.
    But +1 on getting a good Prius-savvy shop with the right type of code reader to really get the codes in the central computer. Accurate knowledge of those is essential to diagnosing problems in a system this complex.
     
    #5 Robert Holt, Feb 11, 2017
  6. anonymous

    anonymous Member

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    Went to autozone last friday and they found two error codes (dont exactly remember what they were and don't have documentation with me right now) and according to the documentation it is likely the gaso.line cap; tightened the cap till click and haven't noticed any more strange behavior. today the check engine light didn't light up anymore :)
    more details tomorrow (it is a pain to type on an i.pod touch)
     
    #6 anonymous, Feb 12, 2017
  7. anonymous

    anonymous Member

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    Error codes were P0455 and P0441.
    Like I said, after getting this info and tightening the cap, no more strange behavior of the engine was noticed and a couple days later the check engine light ceased illuminating. So… it seems that it was just a leaking gaso line cap. We had a similar issue before which went away by itself so perhaps it was the same thing… It's weird; how does an open gasoline system cause the engine to behave strangely, like running at high rpm when stopping and repeatedly speeding up and down when rolling at low speed, etc? :confused:
     
    #7 anonymous, Feb 13, 2017
  8. anonymous

    anonymous Member

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    It was behaving oddly even when power in stealth area and battery at a charge where the engine shouldn't be running at all
     
    #8 anonymous, Feb 13, 2017
  9. anonymous

    anonymous Member

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    Update Jan/Feb 2019 for anyone finding this thread via search: I believe this issue was caused by a vacuum leak caused by the EVAP purge valve randomly binding and being stuck open, as I diagnosed in this thread. The solution is to replace the EVAP purge valve.
     
    #9 anonymous, Oct 25, 2019
    Robert Holt likes this.
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