Small motor or pump running after car is shut down

Discussion in 'Gen 4 Prius Care, Maintenance and Troubleshooting' started by [email protected], Sep 18, 2025 at 3:59 AM.

  1. Racerman15@comcast.net

    [email protected] Junior Member

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    2020 Prius, 50k miles. Gas mileage 52+, power is very good. No operating issues But - several times in the past few weeks I have come into the garage and heard something running from under the rear of the car. It is a small electric motor sound. If I turn on the car in the usual way the sound stops and stays off once the car is turned off. Two times I know that the noise was not present immediately after the car was turned off - but I observed the noise a couple hours later, and not sure when it started or how long it had been running. One time I let it run to see if it would turn off by itself. I checked it after 45 min and it was still going. I am thinking that it might be the hybrid cooling fan, fuel pump, ??? I was hoping for some ideas before I started taking things apart.
     
    #1 [email protected], Sep 18, 2025 at 3:59 AM
  2. FuelMiser

    FuelMiser Senior Member

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    It's normal.
     
    #2 FuelMiser, Sep 18, 2025 at 8:49 AM
    BiomedO1 likes this.
  3. BiomedO1

    BiomedO1 Senior Member

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    Your battery would be DEAD, if something keep running after the car is shut down. How would you find an intermittent problem like that by ripping it apart???

    The car does readiness testing at certain intervals and if it see the FOB in your pocket - it's going to fire everything up. It's like a pre-flight check list before startup.
    Drop you FOBs in a Fairiday bag or throw them in your refrigerator and see if the car does the same when you look-in on it. I know they used to build houses over there with chicken wire mesh to hold up the plaster. That also blocks RF signals, so when you open up a door, a weak FOB signal becomes a stronger FOB signal - indicating to the car that your approaching and likely going to drive her.

    Hope this clears things up.....
     
    #3 BiomedO1, Sep 18, 2025 at 10:01 AM
    Last edited: Sep 18, 2025 at 10:31 AM
  4. Robert21PrimeLTD

    Robert21PrimeLTD Member

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    it’s probably the fuel evaporation leakage check. happens approx. 5 hours after using the vehicle. check your manual.
     
    #4 Robert21PrimeLTD, Sep 18, 2025 at 10:27 AM
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