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2007 keeps dying + Toyota dealer can’t figure out why

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Koko, Jan 10, 2023.

  1. Koko

    Koko Junior Member

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    We have a 2007 Prius, approx. 202k. The radio stops working then a few days later the 12-V battery dies and car lights don’t even go on. Car needs to be jumpstarted and it runs fine for a few days. Then it all happens again.
    The regular battery has been replaced twice within past few weeks. The hybrid battery was replaced a few years ago. Toyota dealer says there are no issues w the electronics, and they haven’t been able to duplicate the issue.
    Any ideas what may be the cause?
     
  2. bisco

    bisco cookie crumbler

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    Sounds like a bad connection. Do you want to buy tools and learn how to do some testing?
     
  3. TMR-JWAP

    TMR-JWAP Senior Member

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    First thing would be to look for a loose connection at the 12v battery terminals and where the (-) cable fastens to the car body.
    If all that is good, seems like the next step would be to determine why (or if) the 12v battery is draining.
    Do you have a good multi-meter?
     
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  4. Koko

    Koko Junior Member

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    We do not have one. Suggestions on brand to buy?
     
  5. Koko

    Koko Junior Member

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    Sure. Suggestions pls.
     
  6. bisco

    bisco cookie crumbler

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    start with a digital volt meter, anything like this:ref=asc_df_B0BGT8XT12

    and measure the voltage at the jump point under the hood
     
  7. Koko

    Koko Junior Member

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    Will do, thanks!
     
  8. edthefox5

    edthefox5 Senior Member

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    There have been reports of the brake backup circuit going bad and putting a constant load on the 12 volt battery. The box has super capacitors that hold a charge and in the event the 12 volt fails while driving it will supply brief power to the braking system to safely stop.

    Its the small metal box that sits right next to the 12 volt battery. The capacitors in that metal box need to be checked for ESR.

    ESR is basically the capacitor failing and starting to act like a resistor. ESR issues are Very very common in electronics. In fact its the main reason the dash combo meter fails in G2's.

    I linked an ESR wiki.

    To test a cap for ESR you need an ESR tester. There hundreds out there I just grabbed one to show you:

    https://www.ebay.com/itm/323878240428?epid=2180686390&hash=item4b68a5c0ac:g:mikAAOSwuNxiHsMY&amdata=enc%3AAQAHAAAA4FQBy4IfdJ7rLjQ%2Fhm5kG37XzGyQwndT8GjdmXXf65FJjre1JhF%2Fe1nbHIXWBSngvJGTW0l9sN4fHWvyfTi6CkF5ZHGxhvaddIkQpLIA%2BF9apD6MaeHqy4XW8F1DwRkmPEkDYYWd1UU9e7rkLuLAEyG1Xq4Ikw8r%2BhAPGmRb%2FwIK6HH0b8EbSmL5NOpwf4q59qbaGv%2BJdiO1lqy33An%2FaIYjufxWyO6e4hFljp6fgY5NcqenuyaGb6wLF%2BX7oU3CW4yo%2B5INRU10TQonz7b24bo8RZSFvP0LEXMmGGcobzTD%7Ctkp%3ABFBMppfb57Rh


    https://en.wikipedia.org/wiki/Equivalent_series_resistance
     
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  9. Koko

    Koko Junior Member

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    So this could be why the radio suddenly stops working while driving…
     
    #9 Koko, Jan 12, 2023
    Last edited: Jan 12, 2023
  10. ColoradoBoo

    ColoradoBoo Senior Member

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    Yep you definitely have a dreaded electrical gremlin going on. Since it's a 2007, my first thought was rust...are any grounds rusty? In the 12-volt system, nothing will worth if the connection has a ground or a bad ground. (There are a LOT of places to check!!) Get a bright light and go through the engine compartment from top to bottom and check any and all grounds. It may require removing some components to get down to the frame but will be worth it if you find it. Also look for any chewed/cut wires (mice, rats, squirrel)
     
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  11. edthefox5

    edthefox5 Senior Member

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    I agree with the rust but the op never included his location so who knows where it lives.

    if your having battery shenanigans the first thing is if you killed the battery by leaving a light on usually it will damage the battery's future ability to take a full charge. They don't make battery's like they used to.

    Easy to check a battery's health:

    Get a voltmeter and with car OFF check the voltage at the front jump point. Write it down.

    With car OFF turn on the hi beam headlights. Let them run for exactly 5 minutes then turn them off. Let the car sit for 2 minutes and then measure the voltage at the jump point again.

    With a very healthy battery it will drop around a half a volt . .5 volts with this somewhat benign load test.

    A soft battery will tank on this test like 2 volts or maybe worse. Its the battery's inability to hold a charge. If battery not to old a recondition may help but I would always be suspicious its going to leave me.

    I do know for sure a healthy battery on a often used G2 lives at 12.6 volts with car off. Anything much lower than that right at the get go I would be suspicious.
     
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  12. Aegean

    Aegean Active Member

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    Why don’t you remove the radio fuse and monitor if the issue comes back? I suspect that something in the radio circuit or the radio unit itself is shorting and drains the battery.
     
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  13. edthefox5

    edthefox5 Senior Member

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    Good point Aegean.

    It made me remember years ago a recall on the G2 with the top Touring model model that had a factory JBL stereo system with its audio power amp under the passenger seat. I think it had a center speaker on the dash too. The audio amp under the passenger seat it's turn on circuit would fault to always on even with the car off.

    It killed many a Prius battery. Do you have leather seats and a JBL factory stereo?
     
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