My 2014 prius won’t start without a jump, even with a new 12v battery. Why?

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Joe W., Aug 21, 2025 at 5:08 PM.

  1. Joe W.

    Joe W. New Member

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    So I have a 2014 Toyota Prius with over 200,000 miles on it. It’s been a great car and I really would like to get it fixed. About a week ago it started showing symptoms that the 12 V battery was going bad. We limped it on for a week or so. When I say that I meant to say we would try and start it and it wouldn’t start on the first button press. We would have to hit the start button a few times before it would actually start. I thought,”easy! Bad 12v battery” and replaced it. That didn’t solve the issue. In any other car I’d say the alternator was bad but as we know Prius’ don’t have alternators. It will start fine off of a jump pack/box or from a car jump start and will drive until the motor shuts off. Once the motor kicks off to switch to the ev battery, it dies. Any solutions to this?
     
    #1 Joe W., Aug 21, 2025 at 5:08 PM
  2. NutzAboutBolts

    NutzAboutBolts Senior Member

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    Any check engine light?
     
    #2 NutzAboutBolts, Aug 24, 2025 at 1:38 AM
  3. Mendel Leisk

    Mendel Leisk MMX GEN III

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    Do you have a multimeter? You could do a rudimentary check of 12 volt battery voltage, and verify connections are solid. There are also electronic load testers ($50~100). A lot of automotive retailers will have these and will test for free.

    could also be issue with the sensor that verifies brake pedal depressed before allowing engine start.
     
    #3 Mendel Leisk, Aug 24, 2025 at 7:48 AM
  4. BiomedO1

    BiomedO1 Senior Member

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    You've got a parasitic drain and/or loose connections on the battery. If it is in deed a battery issue, you should be able to get a replacement at no cost.

    Good Luck.....
     
    #4 BiomedO1, Aug 24, 2025 at 10:47 AM
  5. bisco

    bisco cookie crumbler

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    sounds like a bad inverter. any coolant movement in the inverter reservoir? did you do the ipm fix?
     
    #5 bisco, Aug 24, 2025 at 1:57 PM
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