2006 Prius only starts with jump

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Rhonda124, Oct 22, 2019.

  1. Rhonda124

    Rhonda124 Junior Member

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    Location:
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    Vehicle:
    2006 Prius
    Model:
    II
    So I've had my 2006 Prius for almost three years now, and almost no problems until now. She's sitting at 175,000 miles.
    The car will not start without a jump, except the odd start here and there. It will jump really fast and come on, and will be completely fine until it is turned off again and it does not stall while driving.
    I've checked the 12 V battery, reading 12.6V while the car is off and 13.98V while the car is on, so it is holding a charge and is receiving a charge.
    When the car refuses to start, all of the interior lights and the smart key also refuse to work, so I am pretty confident the starter is alright. I've checked my inverter coolant pump and it seems to be running fine and I've also gone through and checked all of the fuses within the car, and none have blown.
    All of this started a few days after getting my oil changed.
    A few notes: I DIY fixed my combo meter a few months back (best decision I ever made) due to a nonoperational dashboard and I recently had my front tires replaced. My MFD touchscreen doesn't work and I believe the unit has a short in it as well, not sure if it is at all related.

    Does anyone have any ideas in regards to what might be causing this problem?

     
  2. bisco

    bisco cookie crumbler

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    turn the headlights on for 5 minutes. then read the 12v after 4 more hours. report the voltage back here.

    how old is it?

    are you jumping at the battery or jump point?

    are you measuring the 12v at the jump point?
     
  3. TMR-JWAP

    TMR-JWAP Senior Member

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    Touring
    Just.....replace....the....12v....battery...….

    When the car refuses to start, all of the interior lights and the smart key also refuse to work, so I am pretty confident the starter is alright.

    FYI, the 12v battery in a Gen 2 Prius provides power only to energize the electronics and light systems. It has nothing to do with starting the engine. The "starter" is the transaxle, which is spun by the "big" High voltage battery.

    If the 12v battery is weak, the electronics (like the lights and smart key system) will not work. If the electronics can't start, they can't shut the main power relays for the main battery. If the main power relays can't be operated, then the main battery can't spin the transaxle to start the engine.

    The car starts when you jump it because you are energizing the 12v "bus" with a good battery. One the electronics start up, the "inverter" takes over (similar to an alternator) and starts supplying the 12v bus at about 14 v. This WILL try to charge the 12v battery, but a bad battery will not hold a charge. If you check it shortly after shutting off the car, it will appear to have good voltage. Try it again after running the headlight s for a few minutes and you'll probably see drastically different results.
     
  4. dolj

    dolj Senior Member

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    Or ... If the battery is really holding a charge, check the connections in the back at the positive, negative and body earth that they are tight and clean.
     
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