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Prius turning itself on by itself and resetting trip counters and clock

Discussion in 'Gen 3 Prius Main Forum' started by N1ghtfire, Aug 22, 2022.

  1. N1ghtfire

    N1ghtfire Junior Member

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    Hello!
    I have a 2011 Toyota Prius with 200k miles.
    Starting yesterday my car will turn itself back on into accessory mode all by itself after I turn the car off, and it will reset all of my trip data and the clock is reset. The car starts up and runs like normal, but the past few times I shut it off it turns itself back on and resets everything.

    I already checked my 12v battery a couple of weeks ago because for the past few months the TPMS warning light will randomly come on and flash and then turn solid. I read that this could mean a battery in one of the tire pressure sensors is bad, or could be a problem with the 12v. So I took my 12v to AutoZone to have it tested and they said it was in great shape.

    I tried searching the Prius chat and it seems others have had their car do the same things where it automatically turns back on, but none of those threads ever updated with the cause/resolution.

    Does anyone have any ideas, or have had this happen and resolved the issue?

    No error codes on my OBD2
     
    #1 N1ghtfire, Aug 22, 2022
  2. bisco

    bisco cookie crumbler

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    iirc, it is usually a loose connection at the 12v, especially neg to ground
     
    #2 bisco, Aug 22, 2022
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  3. JC91006

    JC91006 Senior Member

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    The TPMS sensor batteries will eventually go bad, just replace the entire set of 4 and you'll be trouble free for another 10 years.

    Amazon sells a set for about $41, look for Roadfar branded sensors for Prius, they work great.

    And for the other problem, you may need an excorcist or a new 12v battery (if it's over 5 years old)
     
    #3 JC91006, Aug 22, 2022
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  4. bisco

    bisco cookie crumbler

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    the 12v might even have an intermittent internal short
     
    #4 bisco, Aug 22, 2022
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  5. Johnny Cakes

    Johnny Cakes Senior Member

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    The Prius can do some funky stuff when there is an accessory with a large battery plugged into the 12v cigarette lighter and the car is turned off. I think bisco has the answer but just throwing this out there.
     
    #5 Johnny Cakes, Aug 22, 2022
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  6. Mendel Leisk

    Mendel Leisk EGR Fanatic

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    Mice?
     
    #6 Mendel Leisk, Aug 22, 2022
  7. N1ghtfire

    N1ghtfire Junior Member

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    So update, all the connections to the battery are solid, but as soon as I got to my campsite I turned my car off and for about one minute it was completely dead and wouldn't turn back on, then it suddenly regained power.

    So now I'm nervous
     
    #7 N1ghtfire, Aug 22, 2022
  8. N1ghtfire

    N1ghtfire Junior Member

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    Is this an actual thing?? Because I have a Jackery 1000 that keep plugged into my car so it can charge while driving.
     
    #8 N1ghtfire, Aug 22, 2022
  9. bisco

    bisco cookie crumbler

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    try disconnecting it and watch the behavior
     
    #9 bisco, Aug 22, 2022
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  10. Johnny Cakes

    Johnny Cakes Senior Member

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    That definitely could be it. Read this thread:
    What is Prius trying to tell me with all this beeping? | PriusChat

    The Prius does not like to be turned off with a substantial battery/draw connected to the cigarette lighter 12v. It goes into ACC mode instead.

    That thread also includes a link to a thread regarding ICE random starting.
     
    #10 Johnny Cakes, Aug 22, 2022
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  11. N1ghtfire

    N1ghtfire Junior Member

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    Thank you! I just read that thread and I think this is exactly what is happening with mine. I've unplugged my Jackery and everything seems alright so far. I'll update if the problem persists without anything plugged into the cigarette lighters.
     
    #11 N1ghtfire, Aug 23, 2022
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