Is my 12V battery on the way out?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by TheNovice, Feb 1, 2016.

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  1. TheNovice

    TheNovice New Member

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    2008 Prius
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    Hi all.

    The red triangle warning and VSC lights came up on my wife's Prius this evening. I accessed the system menu using the headlight trick, and got the following voltages....
    One click start button - 12.1V
    Second click start button - 11.8V
    Second click start button with dipped lights on - 11.0V
    Foot on brake, third click start button, car starts - 14.3V

    Or could it be something more terminal?

    Thanks ahead of time.
     
  2. jdenenberg

    jdenenberg EE Professor

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    Novice,

    You need to read the OBD2 recorded diagnostic codes (your dealer will charge ~$85). You can get the "miniVCI" as a chinese clone for about $25 (eBay) with a pirated copy of Toyota's diagnostic software which works well on an old Windows XT (32 bit) system. It is Techy, but possible to install on a more modern PC. There is also a very capable system for just a bit more. You need a good Blue-tooth OBD2 plug and a copy of the Android app called Torque (the pro version $5 and add Prius specific functions from the web).

    But your 12v battery is either undercharged (many short trips will do this) or is close to needing replacement. It is may not be the cause of the problem alerts that you see so just replace the 12v with one that os fully charged and see if the problems disappear.

    JeffD
     
  3. TheNovice

    TheNovice New Member

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    2008 Prius
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    Two
    Thanks Jeff.

    Took a chance on the battery, and the warning disappeared as soon as I connected the new one! Unfortunately the expansion hole was too small for the pipe, so I had to take it back out again!

    But at least I know it's the battery now.
     
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