'07 Prius won't start, new 12V battery, fully charged

Discussion in 'Gen 2 Prius Technical Discussion' started by TomNar, Jan 18, 2021.

  1. TomNar

    TomNar New Member

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    My 2007 Prius had been sitting several months with a dead 12V battery. I replaced it with a new Toyota battery (S46B24R) from the dealer and charged it fully with a jumper. Battery reads 14.0 and over 12V under load; dashboard lights read normal and the HV battery has 3 bars. But when I hit the power button, I hear a relay click from the rear with no other action. (It did start once and ran for several minutes until it shut itself off, as is normal when idling. But only that once.) There is no ordinary starter motor in this car, so I'm stymied about the next step. I'd like to be able to get the car to the dealer without a tow. Any suggestions?
     
  2. SFO

    SFO Senior Member

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    Welcome to PriusChat!!

    Do you have any OBD2 codes (DTCs) that you can share with us?

    Make sure the MAF sensor is clean, as swapping or disconnecting the 12v battery will reset the mapping.
     
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  3. sam spade 2

    sam spade 2 Senior Member

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    Sounds a LOT like a bad connection at one end of the main power cables.
    Likely the other end, away from the battery.
    But the battery connections could be corroded too.

    Please check that before running off looking for codes to chase.

    Note: the battery itself will NEVER read 14 V or over and neither should a jump pack.
     
  4. royrose

    royrose Senior Member

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    Do you get the ready light? How do you get the dash lights to turn on without hitting the power button?
     
  5. TomNar

    TomNar New Member

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    The dashboard lights turn on normally when the power button is pushed with my foot on the brake pedal: All warning lights flash on, then go out, leaving the ready light, the speedometer (0mph) and the transmission (P) lights only. The HV battery shows three bars. The battery readings I quoted were taken using the service mode on the dashboard screen.
     
  6. strawbrad

    strawbrad http://minnesotahybridbatteries.com

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    This sounds like a high voltage leak. It's hard to be sure from your description. Try disconnecting the 12 volt battery for thirty seconds and then reconnect it. This will clear the codes. If the car starts and runs normally until shut off and then will not restart that is the pattern caused by a high voltage leak.
     
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  7. edthefox5

    edthefox5 Senior Member

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    I agree high volt leak. That's from letting it sit it will tend to accelerate corrosion. Worst thing you can do to an old battery which includes your 12 and the hybrid battery. Everybody's battery's are going dead becasue they stopped driving.

    If you do have a high volt leak a reset of the 12 will fix it but not for long. It will come right back.

    I'm afraid your hybrid battery is going to need a rebuild like just about every other 07 owner including myself.

    Btw, dont need any tools to reset the 12 volt battery just disconnect the thin black wire and the thick black wire that are on plugs in the battery assy mounted to the top of the battery. Use a small screwdriver and press the white tab on the plug and pull the cable out.

    The thick black wire is the 12 volts to to the front jump post the small is the Inverter sensing wire. After that first time you try to start all the dashboard lights will come on. Do it again see if it starts.

    And start reading the thousands of battery posts on this site to make your decision..
     
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