High temp warning light is always on

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by mmadarling, Jan 13, 2019.

  1. mmadarling

    mmadarling Junior Member

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    I bought my 2010 Prius in July 2017 with 130k miles. I drove off and noticed the high temp warning light was on. I never bothered to ask the dealer about it. I had the coolant level checked and it was fine.
    It's been on ever since. Now my Prius has 164,000 miles.
    I've assumed this whole time that it isn't accurate and is some type of error. How can the coolant temp be high the instant I turn my cold car on, every single time?Also, the check engine light has never come on.
    Any suggestions?
     
  2. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Please provide a photo of the lit warning light.
     
  3. Pluggo

    Pluggo Senior Member

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    Sounds like you have a bad temperature sensor or maybe a defect in the cable that goes to it. A scanGuage or any number of apps can give you the engine temperature when you want it.
     
  4. mmadarling

    mmadarling Junior Member

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    I'm home from work sick but I'll snap a pic when I drag my body out of the house again.

    I hope that's all it is. Thanks!
     
  5. GrGramps

    GrGramps Active Member

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    In the meantime, if the engine should overheat, you may not get an early warning. Be cautious!
     
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  6. sam spade 2

    sam spade 2 Senior Member

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    Yes.
    Don't make a mistake like that ever again.
    You should have returned to the dealer as soon as you noticed it.

    Now you likely will have to pay to fix it.
    And it really should be fixed.
     
  7. mmadarling

    mmadarling Junior Member

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    Here's a pic of it. It's always lit up.
     

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  8. Patrick Wong

    Patrick Wong DIY Enthusiast

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    1. Check the coolant level in the engine coolant reservoir and the inverter coolant reservoir now.
    2. It is possible to determine engine and inverter coolant temperatures by using Mini VCI (Toyota Techstream clone) so that you can see which system is reporting the overheating condition.
    3. Once you know which system has the problem, then you could investigate whether the associated sensor is at fault, or the wiring harness has a short, or ??
    4. It would be good if you could resolve this issue. If the powertrain is actually overheating, how would you know, until you see smoke rising from the hood or the car dies. You won't be happy if permanent damage is caused to the engine or inverter because of this.
     
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  9. mmadarling

    mmadarling Junior Member

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    I'll do the first thing. Not sure how to do the second thing.

    Very good point that I won't know if it actually does overheat since it's always on.
     
  10. Absalom

    Absalom Junior Member

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    You drove 30k with a malfunctioning temp sensor?? Yikes :)
     
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