Key fob low battery warning after installing new battery

Discussion in 'Gen 4 Prius Care, Maintenance and Troubleshooting' started by Zipy, Feb 6, 2022.

  1. Zipy

    Zipy Junior Member

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    2016 Prius. Had low battery warning. Replaced battery and still had the warning. Tried the spare fob and same thing even with a new battery in it too. I even tested the batteries and had 3+ volts in both of them. I can’t believe that both fobs would have gone bad, especially since the spare fob has never even been used. Something in the receiver gone bad? Anyone ever encountered this? Of course it’s out of warranty and I imagine mega $$$$ to fix.
     
    #1 Zipy, Feb 6, 2022
  2. bisco

    bisco cookie crumbler

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    check the 12v health
     
    #2 bisco, Feb 6, 2022
  3. ColoradoBoo

    ColoradoBoo Senior Member

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    Do you store the key fobs near the vehicle or inside the vehicle? They have little radios and will activate if they sense a vehicle nearby and will drain the battery pretty quick. (Look at your key fob when walking through a parking lot...when you walk by another Toyota a little red light will blink!)
    I change out our fob and garage remote batteries yearly...else they seem to go out in the middle of winter at the worst time possible!
     
    #3 ColoradoBoo, Feb 6, 2022
  4. Zipy

    Zipy Junior Member

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    12 volt is good. Installed a new one about a year ago. As far as where I store the fob, pretty much the opposite end of the house from the car.
     
    #4 Zipy, Feb 6, 2022
  5. bisco

    bisco cookie crumbler

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    can't be the 12v then, they never go bad that fast, or lose voltage for any reason.

    try disconnecting the neg for a minute to reset everything
     
    #5 bisco, Feb 7, 2022
    ColoradoBoo likes this.
  6. Purrius

    Purrius Member

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    I keep all of my fobs in a Faraday cage at home. (In this case that translates to an empty pokémon card tin.:LOL:) A cheap and handy solution for mitigating battery drain.
     
    #6 Purrius, Dec 4, 2024
  7. BiomedO1

    BiomedO1 Senior Member

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    I do the same, When I pull my keys out of my pocket - it goes into a Faraday bag. This also prevent thieves from using a signal booster to access and try to steal the car.
    I've been getting an intermittent FOB battery low message on my dash for the last month. Just got around to replacing the battery today. I'll see if that stops the intermittent message. First FOB battery replacement in 4 years.
     
    #7 BiomedO1, Dec 5, 2024
  8. Purrius

    Purrius Member

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    Definitely. I actually started doing it back in Oregon, back then it wasn't kind of sort of maybe technically illegal to steal a car. (Just remember to bring your Crime Committing Kit!)

    What brought me to this topic today was trying to get an answer for my friend. He owns a 2020 and asked me
    "Did you encounter such behavior of Prius FOB when it constantly shows "low battery, replace" even few days after replacement. And the FOB keeps working for months despite of this warning. It started doing that about 1.5 year ago."

    I suggested the Faraday cage and we'll see how that goes.

    I also saw people in Subaru forums mentioning perhaps fobs can get "stuck" in Battery Saving Mode when the battery is changed. I'm curious about this hypothesis.

    (How to Program a Toyota Key Fob)
    How to Program a Toyota Key Fob | Keith Pierson Toyota
     
    #8 Purrius, Dec 5, 2024
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