Wierd sound coming from underneath rear after parked in garage for six hours

Discussion in 'Gen 4 Prius Main Forum' started by jtg61, Feb 5, 2017.

  1. jtg61

    jtg61 Member

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    I went into my garage about six hours after I parked my Prius and I head a weird humming sound coming from the rear of the vehicle where the Lithium Ion batteries are. It sounded like maybe a fan was running, I'm not sure. It just seemed really weird that anything would be running under the rear of the vehicle six hours after I parked it in the garage. Why would something be running on my Prius after it was parked for so long? Any ideas? Is it something I should be concerned about?
     
  2. alanclarkeau

    alanclarkeau Senior Member

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    No idea really - did you have your smart key in your pocket? And was the car locked?

    If I have the key in my pocket and walk past the car - if it's at night, I can see the interior light turn on. My hearing isn't real good - so I'm not sure about noise - but it sure knows I am there.
     
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  3. jtg61

    jtg61 Member

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    No smart key in my pocket. I was in my garage getting beer out of the fridge when I hear the buzzing sound coming from underneath the rear of the car, like an inverter or fan was running hours after it was parked. Never heard this sound before.
     
  4. bisco

    bisco cookie crumbler

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    it's an evap check for pollution control. weirded me out the first time i heard it. can you say 'christine'?:sneaky:
     
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  5. jtg61

    jtg61 Member

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    It runs this check hours after you've parked your vehicle? Very weird, but good to know it's normal. Thanks!
     
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  6. alanclarkeau

    alanclarkeau Senior Member

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    how long did it go for? Your fuel tank is different from ours here. Ours doesn't have the pressure lock or whatever it's called.
     
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  7. bisco

    bisco cookie crumbler

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    right? not sure what the delay is for, maybe it's some kind of leak down test.
     
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  8. jtg61

    jtg61 Member

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    It ran for about 5 minutes and then stopped. I've gone out to the garage periodically and haven't heard it since.
     
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  9. bisco

    bisco cookie crumbler

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    same here, you have to time it right. i've only heard it a few times in almost 5 years.
     
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  10. Colin Jones

    Colin Jones Member

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  11. ETP

    ETP 2021 Prime(Limit),Highlander HYB Plat,B52-D,G,F,H

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    It needs beer.
     
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  12. kithmo

    kithmo Couch Potato

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    It was humming because it had forgotten the words :LOL:
     
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  13. sorka

    sorka Active Member

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    Mine 2019 does this nearly daily. It's doing it now and has been going for hours. Worried that it's going to drain the 12v battery....unless it runs on the main traction battery?
     
  14. ChapmanF

    ChapmanF Senior Member

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    I'm sorry I don't have the 2019 Repair Manual handy. This is the timing chart of the evap self test from Gen 3. Adding up the times along the bottom shows the whole test is done in 23 minutes 10 seconds tops, with the leak detection pump running most of that time (all but the first minute). It's a small pump and runs on the 12 volt system and Prii have been doing it for years without issues.

    Again, I'm looking in a Gen 3 manual, so it's possible they changed something for Gen 4, but "hours" definitely doesn't sound right.

    evap.png
     
  15. Colin Jones

    Colin Jones Member

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    The manual also states this though:
    "Approximately five hours after the hybrid system is turned off, you may hear sound coming from under the vehicle for several minutes."
    upload_2021-5-31_15-23-40.png
     
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  16. Data Daedalus

    Data Daedalus Senior Member

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    I suspect if your Prius detects your smart key when you walk close by, and reacts accordingly by turning the interior lights on, it will automatically begin to prime the vehicle “for lift off” so to speak.

    Even my old 2008 Gen 2 without the smart key (UK) will initiate a pre-startup sequence (charging the brake master cylinder I think), as soon as I open the drivers door.

    I think this is perfectly normal and every version of Prius does something like this.

    Whenever I’ve got home from my commute, parked, got my stuff out of the trunk and I’m walking to the house, my Gen 2 proceeds to make a series of distinctly peculiar noises somewhat akin to the Millennium Falcon venting plasma after it has landed, and the crew are walking away.

    I look back half expecting it to be venting gasses like that fictional YT-1300 Freighter. The noises never fail to mildly amuse me though .

    Your Prius is perfectly fine, and doing exactly what it’s been programmed to do…..


    Source: iPhone 12 Pro Max 512GB ? Pro
     
  17. BellevilleMXZ

    BellevilleMXZ Junior Member

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    Evap. system(charcoal canister and related parts that capture fumes from fuel tank) doing a test. I noticed its even mentioned in my manual
     
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