12V error

Discussion in 'Gen 4 Prius Care, Maintenance and Troubleshooting' started by TSaxman28, Aug 10, 2026 at 8:40 AM.

  1. TSaxman28

    TSaxman28 Wandering Minstrel

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    For the last two days I went to start my car and got an error message saying, “Low 12-Volt Battery, Apply Parking Brake Securely While Parking…”. All the accessories are working, all lights come on, but when I press the brake pedal and try again I get another message saying, “Not Ready to Drive, Depress Brake Pedal and Push Power Switch to Start.” Yesterday I called AAA and then gave me a jump but said the battery was showing 12.3 volts.

    Anybody have any idea what is going on?
     
    #1 TSaxman28, Aug 10, 2026 at 8:40 AM
  2. rjparker

    rjparker Tu Humilde Sirviente

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    It is possible to have a battery that reads 12.3v but then falls quickly when trying to Ready the car.

    You need a load test on that 12v battery. If it fails you need a new battery.

    Most auto supplies can do it but you may want to move the covers out of the hatch area first.
     
    #2 rjparker, Aug 10, 2026 at 9:11 AM
    BiomedO1 likes this.
  3. TSaxman28

    TSaxman28 Wandering Minstrel

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    Thanks for the quick reply. Sorry to be a little thick but why would I need to move stuff out of the hatch area?
     
    #3 TSaxman28, Aug 10, 2026 at 10:06 AM
  4. rjparker

    rjparker Tu Humilde Sirviente

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    You don't need to on a gen4
     
    #4 rjparker, Aug 10, 2026 at 10:10 AM
  5. BiomedO1

    BiomedO1 Senior Member

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    If you continue to get that second error message; your brake pedal switch may be intermittent. That may become dangerous; since that also drives your brake lights.
    I've developed the habit of hitting my hazard lamps when I hit slow moving traffic on the interstate - don't want someone coming around a blind curve thinking I'm going full speed - when traffic is only creeping. I know I've avoided a few collisions; because I've seen several cars lock-up their brakes in my rear view mirror.
     
    #5 BiomedO1, Aug 10, 2026 at 10:42 AM
  6. TSaxman28

    TSaxman28 Wandering Minstrel

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    Thanks for all the super fast replies. AAA just left and his diagnostic show some dead cells in the battery. Considering that it's original battery I'm not surprised that was the issue. Not bad for lasting 7 years.
     
    #6 TSaxman28, Aug 10, 2026 at 11:56 AM
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