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2015 Prius C will turn on but won't get into Ready Mode.

Discussion in 'Prius c Main Forum' started by Stoicadjacent, Oct 28, 2023.

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  1. Stoicadjacent

    Stoicadjacent New Member

    Joined:
    Oct 28, 2023
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    Location:
    Indiana
    Vehicle:
    2015 Prius c
    Model:
    Four
    My Prius sat for 1 month without driving. When I tried to start it, it made some electrical noises, but would not start. The door locks would not work. It was clear the (12v) battery was dead.

    I jump started it using the terminal in the fuse box designed for that purpose. Started right up and got into ready mode.

    I figured the battery would charge with a half-hour of driving, freeway and backstreets). When I arrived at my destination, I turned it off. I mediately tried starting it again and it just made those electrical noises and the display did not fully load.

    Jump started it again. Started up, ready mode, etc. Drove it to auto parts store. Removed the battery. Had it tested. Said it was good but has no charge (3 years old). They charged it for an hour and tested it. I connected battery again. I thought it was going to start up because the car started up display wise like normal and made the normal electrical sounds. It just won't enter ready mode.

    Let it sit and hour or so, went out to start it again and the display fires up, air works, radio works, headlights work. Wouldn't get into ready mode. Cycled the startup again, this time it randomly went into ready mode. Drove it around the block. Parked it and turned off and on again testing accessories. It cycled through another 3-4 times, but the last attempt wouldn't turn the radio on and the display started to flicker. All the flashlights remain on, except that rogue time it went into ready mode.

    Is this a bad 12v battery? What could be going on here? Any help would be much appreciated!
     

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    #1 Stoicadjacent, Oct 28, 2023
  2. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

    Joined:
    May 12, 2018
    7,173
    6,718
    1
    Location:
    Pennsylvania
    Vehicle:
    2018 Prius c
    Model:
    Two
    The Prius charging system is a little weird- it does not matter whether you drive the car or leave it sitting still in READY mode- it will charge the 12v battery the same in both circumstances.

    On the other hand, half an hour just isn't long enough to charge one that has been brought particularly low.

    An hour is better, but since that was done with the battery out of the car that means there's a chance the terminals were not adequately tightened when the battery was reinstalled. That gives you a whole other possible reason for fail-to-READY.

    Check the terminals to make certain they are properly tight. Test the battery voltage with a meter to eliminate guesswork. Then you'll be getting somewhere.
     
    #2 Leadfoot J. McCoalroller, Oct 29, 2023
  3. ChapmanF

    ChapmanF Senior Member

    Joined:
    Mar 30, 2008
    24,012
    15,614
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    Location:
    Indiana, USA
    Vehicle:
    2010 Prius
    Model:
    IV
    My Gen 3 sometimes even seems to reduce the charging voltage while in gear and moving, and increase it when stopped or in Park. I assume they've picked a strategy to milk the most motion out of every joule when moving, and then when not moving anyway, charge the battery with more of the energy that might otherwise be wasted.

    So it might even be that driving around is a slower way to recharge the 12 V than just sitting in READY.
     
    #3 ChapmanF, Oct 29, 2023
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