Needing help to find 12v battery status on MFD

Discussion in 'Gen 2 Prius Main Forum' started by Tynyyn, Apr 21, 2021.

  1. Tynyyn

    Tynyyn Junior Member

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    I posted tales of my 12v woes a couple of months ago and within those threads I "kinda" remember someone being able to check their 12v battery status by pressing a few buttons on their MFD. Could someone tell me the secret button pushing procedure or at least point me to the correct thread?

    I'd also like to say thanks to the folks who reply to my quirky inquiries are quite the geniuses. It always impresses me the sheer depth of knowledge ya'll have. Plus the overwhelming ability to help hapless dolts who cannot perform a simple thread search. : )
     
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  2. ChapmanF

    ChapmanF Senior Member

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    There are a couple ways to do it. One is to press the Display button, and then tap the top and bottom left corners of the "frame" that comes up on the MFD screen: top bottom top bottom top bottom.

    There's another way that involves flicking the taillights on and off, but I forget the details.

    Either way, once you get to the diag menu, it's the Vehicle Signal Check screen that you want. You'll see the voltage displayed there. Many of us find it to read around half a volt lower than what you would see with a meter at the battery, maybe a little more.
     
  3. edthefox5

    edthefox5 Senior Member

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    Use the Search forums. Link up top. It’s just a sentence in blue along the top of the page.
    Click on that and in the search bar put

    how to check 12 volt battery on mfd

    or any other check. Works exceptionally well this is a very searched site just about every malady on your car has been explored here ad nauseum
     
  4. jdenenberg

    jdenenberg EE Professor

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    Here is a link on how to use the MFD to test your 12v Battery: Weird stuff happening? MPGs dropping? Test The Battery | PriusChat

    JeffD
     
  5. dolj

    dolj Senior Member

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    Just a small point of clarification, it is only necessary to switch the side lights on/off 3 times, not the headlights. Your headlights will appreciate that in the long run.
     
  6. Mendel Leisk

    Mendel Leisk Sand Pounder

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    ^ This.

    You’re going to get more accurate voltage readings, and not muddled by the car being on, using a digital multimeter. Testing at the battery posts vs (say) at the under-hood jump points, you also will see any voltage drop, which would point to poor connections or damaged wiring.

    With an electronic load tester you would take it up another notch, go from just testing voltage to testing the battery’s Cold Cranking Amps , it’s viability.
     
  7. ChapmanF

    ChapmanF Senior Member

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    I have a houseful of specialist instruments, but a lot of times the most useful instrument is the one you have with you when it's needed. I have a laptop with Techstream, but if I get a warning light on a road trip, I use a jumper wire and light blinks to get the codes because a piece of wire fits in the glove box. If I'm curious about the battery voltage, a lot of the time I'll just look at the ScanGauge sitting over my steering column, or pull it up on the MFD and add about half a volt in my head. (Yes, that difference also exists between the MFD reading and the number shown on the ScanGauge 30 cm to its left.) If you've ever compared the MFD reading to a trusted meter reading on the battery at the same time and made note of the difference then, adding that in your head to later MFD readings will get you even closer, and close enough for nearly all practical purposes.

    It's like being told by your doc it's a good idea to drink about 2 liters of water a day. That's probably advice worth following, but if you're carrying around a graduated cylinder so you can tell the difference between 1.99 and 2.01 l, you might be going a bit overboard with the significant figures.
     
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  8. Mendel Leisk

    Mendel Leisk Sand Pounder

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    You don’t use a graduate as a tumbler...? :whistle:
     
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