Prius Turns Back On After Shutdown

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by thelonelypuppet, Sep 16, 2021.

  1. thelonelypuppet

    thelonelypuppet Junior Member

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    Hey. Was hoping I wouldn't be back here again

    Same as usual: 2008 Toyota Prius. In June of 2021, I got my hybrid battery worked on/replaced (red triangle of death; it was a ghastly $2100 repair).

    Everything was fine for a few months. I've been driving it pretty regularly (close to daily) for 40-minute round trips.

    Recently, my car is doing this strange thing where when I turn it off (foot on brake, press power button), the car will shut down for a moment and then immediately come back on.

    A few things to note:
    1. I'm certain I'm not somehow pressing the button twice.
    2. I am able to turn the car off after this happens. I think it might be immediately rebooting into accessory mode, because I have to press the power button twice to get it to turn off.
    3. This happened a few times for 1-2 weeks, then last week, I had to get my car jumped because the car wouldn't turn on at all.
    4. The car isn't showing any lights/notices that are relevant to this problem (I have a tire pressure light on because the sensor is dead, and when I got my oil changed, the mechanic never reset the light for that)
    5. The problem is somewhat intermittent (I think I notice it primarily in the mornings after driving for about 20 mins)

    Any thoughts on what is causing this? Hoping and praying it is not a hybrid battery issue.
     
  2. burrito

    burrito Member

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    How old is the 12V battery? You can get it load tested for free at any auto parts store.

    I suppose it could also be the actual button.
     
  3. davecook89t

    davecook89t Senior Member

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    Pressing the power button with foot on the brake is necessary to turn the car on, but to turn it off, foot on the brake is not necessary. Have you tried turning it off without your foot on the brake?
     
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  4. thelonelypuppet

    thelonelypuppet Junior Member

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    The 12v is roughly 1.5-2 years old. I had it replaced a few times due to various other issues (my post history goes into that some)

    I actually just tried this after reading that wasn't necessary. My car shut completely off (like, no power, doors wouldn't lock or unlock, nothing)

    The car came back on just fine, but with the clock reset to 1pm.

    I'm thinking something must have happened between when I parked this morning and when I left work, too, because the clock was off by two hours. I'm not sure if that happened immediately after I turned off the car this morning and had the issue I described earlier or if it happened at some later time.
     
  5. edthefox5

    edthefox5 Senior Member

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    If you killed the battery once by leaving a light on that battery is now toast and will never hold a full change again. And will do stupid things like your seeing.

    All dead battery folks have one thing in common. They do not arm there car every single time they get out of it and if leaving it for the night arm the car and then peek inside to see if any lights are on.Especially if in the garage.

    Been doing that for 14+ years on my G2 have never had a dead Prius battery yet.

    And exposing a Prius to a 12 volt jump done wrong can total that car. See it all the time on this site.Do all you can to avoid that.
     
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  6. davecook89t

    davecook89t Senior Member

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    If the battery checks out good at the front jump points (12.5V or so with a multimeter, after resting with the hood unlatched so you don't have to open the doors, not a real health test, but a quick and dirty one), make sure the negative to ground cable at the battery has not come loose.
     
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  7. dolj

    dolj Senior Member

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    ... and also check both terminal clamps on the posts of the 12 V battery are clean and tight.
     
    #7 dolj, Sep 17, 2021
    Last edited: Sep 17, 2021
  8. jerrymildred

    jerrymildred Senior Member

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    I'm thinking that the root problem is a flaky power button that's giving you double presses.

    As @davecook89t pointed out, there's no need to put your foot on the brake to shut off the car (or any car that I've ever driven). If the button is bouncing and your foot is on the brake, the car will go back into READY mode. If your foot is not on the brake and the button bounces, it will go into ACC mode. If you don't notice that, you'll probably have a dead 12V battery when you come back to the car.

    Those start buttons have been known to fail.
     
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  9. TMR-JWAP

    TMR-JWAP Senior Member

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    This is likely a loose connection either at the 12v battery terminals, 12v (-) chassis ground connection or where the main cable connects to the underhood fuse box.

    Slightly shortened.....
    If you killed the battery once by leaving a light on that battery is now toast and will never hold a full change again. And will do stupid things like your seeing. And exposing a Prius to a 12 volt jump done wrong can total that car. See it all the time on this site

    There are days when I wonder if you live in a different reality.
     
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  10. edthefox5

    edthefox5 Senior Member

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    Funny I feel exactly like that with you.
     
  11. thelonelypuppet

    thelonelypuppet Junior Member

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    Hi all, update.

    Car was doing fine for approximately 1-2 weeks after I had it serviced--they said it was a faulty positive terminal that needed to be replaced.

    I am now sitting in a grocery store parking lot with the red triangle, brake, exclamation point, ABS, VSC, and check engine lights on. The car won't even shift gears.

    I'm getting really tired of these battery issues.
     
  12. bisco

    bisco cookie crumbler

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    then it might be time to take it to an auto parts store for a load test
     
  13. dolj

    dolj Senior Member

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    This does not necessarily mean that you have 'battery issues', although it could simply be that. Go get your battery charged and then tested to rule out whether it is good or bad, as suggested by bisco in post #12. Then move on and get the codes read, if they are still present. You will then be able to move on to get the necessary repairs.
     
  14. thelonelypuppet

    thelonelypuppet Junior Member

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    You're definitely right; it's just the last time this happened, I had to make that huge hybrid battery repair.

    I really appreciate y'all and your advice. I was just super frustrated about the situation (less so now, but still definitely aggravated). This is the third time the car has been in the shop in as many months.
     
  15. dolj

    dolj Senior Member

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    The only way to make the car reliable is to replace the hybrid vehicle battery with brand new modules. If you continue to have piece-meal work done to replace a module here and there it might hold for a few months but will progressively become worse and will continually be in the shop getting repairs.

    But sort out the 12 V battery first.
     
  16. thelonelypuppet

    thelonelypuppet Junior Member

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    Update:

    The mechanic/hybrid specialist ran the codes for the vehicle and said it was throwing codes to do with the hybrid battery and the transmission (don't know the exact codes). They reset the system to get the car out of limp mode and the car is no longer showing the lights or codes. I told them to hold onto the car for a couple of days; they are going to drive it every couple of hours to see if any of the issues return.
     
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  17. thelonelypuppet

    thelonelypuppet Junior Member

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    new update:

    Codes came back on during one of the test drives (which I'm not surprised about). They're keeping the car for further tests I guess.
     
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