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2007 Prius starts but having 12V issues

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by prius300k, Nov 23, 2023.

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  1. prius300k

    prius300k Junior Member

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    2007 Prius - 305K miles - 12V battery installed 4/2020

    Car starts, runs, headlights work, and both display screens are functional.
    What has failed is the radio, interior lights, FOB starting, MPG resetting, door not beeping when open, gas gauge blinking at 1 bar, VSC is lit up.

    Ran the battery self-test and results were 11.7 ACC/ 13.6 Power mode. I purchased
    CTEK - 40-206 MXS 5.0 and after completion, the results were 12.1 ACC/13.7 Power

    The Dome fuse under hood tested Ok with ammeter, I tested all the fuses in that under hood fuse box without issues.

    Can the car be driven in short trips while testing? 3.5 years short life for a 12V battery?
    Any assistance is appreciated.

    Thank you
     
    #1 prius300k, Nov 23, 2023
  2. bisco

    bisco cookie crumbler

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    that is fairly short, but not unheard of. and the voltage will be higher with everything off.

    you may have a problem with something besides the battery, and the vsc means you have a trouble code trying to tell you something
     
    #2 bisco, Nov 23, 2023
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  3. dolj

    dolj Senior Member

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    Double-check the AM2 fuse.

    Check all fuses in the interior fusebox, under the dash, driver's side as well.
     
    #3 dolj, Nov 23, 2023
  4. mr_guy_mann

    mr_guy_mann Senior Member

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    It sounds like you have several unrelated problems. You haven't given much history on this car or the problems it has. Did you just buy the car? Has it been sitting for a long time? Was this stuff all working but suddenly went inoperative all at once?

    A weak 12V can cause problems BUT it has to be very weak (almost to the point where the car won't turn on at all). The should be a number of low voltage and comm error codes stored in multiple ecu's.

    In reality, as long as the voltage at each ecu stays above 9-10V as the car is powering up, then it's not THE cause of your faults. After going ready, hge DC-DC converter supplies 14V to power all low voltage systems. (By all means though, have the 12V charged and tested)

    If the VSC light is on, then scan all the systems on the car for codes. Here's a thread that reviews some scantool apps and devices.

    https://priuschat.com/index.php?posts/3290690

    Fuel gauge that has 1 flashing bar (most/all the time) is likely a failed level sensor in the fuel tank assembly. Remove the rear seat base and the access panel to test sensor resistance at the tank connector with a multimeter. See the service manual for test procedure. (Use the search function on the Gen2 forums to learn about where to find the service manual)

    Dome light; is the bulb good? Is there (+) power and (-) ground at the bulb socket? If not you need to look at the wiring diagram (in the service manual) to see where each circuit comes from.

    For each problem, look at the wiring diagrams to see what that system needs to work. Maybe there's a common circuit, or not.

    Posted via the PriusChat mobile app.
     
    #3 mr_guy_mann, Nov 24, 2023
    Last edited: Nov 24, 2023
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  5. prius300k

    prius300k Junior Member

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    Checked all fuses under the drivers dash. no issues there.
     
    #3 prius300k, Nov 30, 2023
  6. prius300k

    prius300k Junior Member

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    Have had the car since 12/2012. No sitting, it gets about 150 miles /week. Yes, all inoperative at once.
    I've run it thru the CTEK - 40-206 MXS 5.0 charger and maintainer. Is that enough of a charge/test?

    I haven't got to these yet.
     
    #4 prius300k, Nov 30, 2023
    Last edited by a moderator: Dec 1, 2023
  7. dolj

    dolj Senior Member

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    Yes, that should be enough to charge the battery, but you still need to do a load test of some sort to confirm the battery is capable of holding its voltage above 10,5 V and preferably above 11.7 V with the load (5-10 Amps) applied for 10 or 15 minutes. If the battery drops below 10.5 within 15 minutes, the battery needs replacing.
     
    #5 dolj, Nov 30, 2023
    Last edited: Nov 30, 2023
  8. prius300k

    prius300k Junior Member

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    I ran it in test mode and left it on for too long, about an hour, and everything was then off. No starting in diag mode or power mode. No charging with charger/maintainer. Will need to get it jumped.
     
    #6 prius300k, Dec 9, 2023
  9. prius300k

    prius300k Junior Member

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    Attempted a jump thru AAA but it did not start. It seemed to start with no warning lights showing but after shutting it off and back again, no power at all.
    The machine said "Alternator has low output" :)
     
    #7 prius300k, Dec 9, 2023
  10. dolj

    dolj Senior Member

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    If by test mode you mean the Vehicle Signal Check screen, then that probably was not the best Idea.

    The load test I mentioned is best done with the car OFF and the battery voltage tested using a voltmeter directly on the 12 V battery in the back, or the jump points at the front.

    Your 12 V battery more than likely needs replacing.

    I'd be wanting to see the voltage on the hybrid vehicle (HV) battery which can be done using a capable scan tool (see reviews of scan tools here).
    It would be better for us to know the actual code the guy pulled. Was it P0A09?
     
    #8 dolj, Dec 9, 2023
    Last edited: Dec 9, 2023
  11. prius300k

    prius300k Junior Member

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    Was unavailable to check anything else the past couple weeks. I removed the battery from the '07 and was going to move my '12 Prius battery to the '07.
    Before I switched it, I tested the disconnected '07 battery and it registered under 4 volts. I ran it overnight connected to a CTEK - 40-206 MXS 5.0 and after it finished, it is showing 12.8 volts on the multimeter. Was going to reinstall it in the '07 Prius in the morning to test it out.
     
    #9 prius300k, Dec 28, 2023
  12. prius300k

    prius300k Junior Member

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    After much delays with weather and sickness,
    I tested by moving my 12V battery (less than 2 years old) from my 2012 Prius to my 2007 Prius.

    No changes to the issues I was having:
    no interior lights, no radio, no clock, no keeping of mpg, VSC on display.

    Headlights and displays do work. Fuses all tested working.

    Is it just a matter of time, if I decide to drive it again, for it to shut down while on the road? I hoped a newer battery might have been the fix for it. At 305K miles and 17 years old, am at the point of calling it a day for it. It has been a great car and lasted longer than I thought.

    Thanks for your opinions.
     
    #10 prius300k, Mar 13, 2024
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