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2018 Prius Temperature Warning Light turning on

Discussion in 'Gen 4 Prius Care, Maintenance and Troubleshooting' started by Dharma1212, Mar 27, 2024.

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  1. Dharma1212

    Dharma1212 New Member

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    Recently I noticed that when I am driving to work in the morning and I have the heater/defrost on my temperature warning light will turn on when I come to a stop and disappear as soon as I start driving. I took it to the dealership for 100k maintenance and asked them to check if I had a coolant issue related to this. They said they were not able to find any leaks and my coolant is full. I had them test drive with the heater on and they said they did not see the light come on. I was reassured everything seemed fine but then two days later the light reappeared when I was on my way to work. I am worried I am messing up my engine and am not sure what else could be wrong.
     
    #1 Dharma1212, Mar 27, 2024
  2. bisco

    bisco cookie crumbler

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    did they run a scan for trouble codes?
     
    #2 bisco, Mar 27, 2024
  3. ChapmanF

    ChapmanF Senior Member

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    Temperature that goes high only when the car is stopped may suggest a problem with the cooling fans behind the radiator.

    Once the car is moving, the relative wind moves enough air through the radiator to cool it without the fans.
     
    #3 ChapmanF, Mar 27, 2024
    Dharma1212, Doug McC and FuelMiser like this.
  4. Dharma1212

    Dharma1212 New Member

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    I think they did but they said they couldn’t recreate the issue and cause the light to come on
     
    #4 Dharma1212, Mar 28, 2024
  5. Dharma1212

    Dharma1212 New Member

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    I was driving this morning no heater or defrost on and it sadly came on again so I don’t think the issue is related there. The dash temperature read 55 degrees Fahrenheit and it does seem like this issue is restricted to the morning when it’s cold
     
    #5 Dharma1212, Mar 28, 2024
  6. Mendel Leisk

    Mendel Leisk EGR Fanatic

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    How the coolant level, in the engine reservoir, under the hood?
     
    #6 Mendel Leisk, Mar 28, 2024
  7. Dharma1212

    Dharma1212 New Member

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    I checked and it’s full, they made sure it was full when I was at the dealership last week as well
     
    #7 Dharma1212, Mar 29, 2024
  8. Rwc86

    Rwc86 New Member

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    On the generation 4s, there’s a coolant temperature sensor above where the exhaust manifold is. I’ve repaired 4 cars where the wires have broken directly at the sensor plug. It will cause the high temperature light to come on, and on the diagnostic system I was using it threw out no codes. The light was on even when the engine was cold and freshly started. It’s worth taking a few moments to check if that might be your issue too
     
    #8 Rwc86, Jun 18, 2024
    Mendel Leisk likes this.
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