Incessant beeping cured (maybe) by battery reset

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by eliotb, Nov 24, 2025 at 8:17 AM.

  1. eliotb

    eliotb Junior Member

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    My question is less about the noise than the so-far unfindable source. My 2014 Prius with 102k miles started beeping a few days back, incessantly — every 3 seconds whether the car was running or turned off and locked up. After it beeped during shutdown overnight I tested the 12v battery. It tested fine. A scanner seemed to find no codes, though i will see if Dr. Prius finds anything. The beeping did not trigger any warning lights. However, the imobilizer system light flashed per normal and it seems to flash at the same 3 second interval as the beeps.

    The beeping finally stopped after a 15-20 minute period with the negative terminal off the 12v battery. Given my automotive luck, the beep will probably return.

    Suspects range from a faulty door or hatch microswitch to (maybe) a failed or failing front passenger airbag sensor in that seat. My disabled wife is horribly obese from her ailment and at times the air bag ‘on’ light fails to illuminate, though it will light up for smaller individuals.

    Any thoughts as to the source/cause/potential code of the mystery beeps?

    Otherwise, the traction battery is down to about 60% capacity, the mileage is down and I’m entertaining thoughts of trading it next year or dumping maybe $4k into it for a replacement battery, new water pumps and plugs and driving it two or three more years. It’s our runabout car and gets about 7-8k a year. I have a big, beautiful, 2003 Jaguar Vanden Plas for fun. :)

    Eliot/Northern VA
     
    #1 eliotb, Nov 24, 2025 at 8:17 AM
  2. ChapmanF

    ChapmanF Senior Member

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    That's a puzzler.

    One approach I might take would be to try to pinpoint the physical source of the beep. Is it louder inside the cabin or out? The car has a variety of beep-making devices: under the left fender, under the hood, several under the dash.

    I know it can also hard to pinpoint the source of a brief, high-pitched, beep (cf. "which smoke detector needs the new battery?!"). But once you can point to the beep-making device that's making it, you can look up that BMD in the wiring diagram and find out what system it belongs to.

    There was a thread a lot like this a while back, that went on for a bunch of posts, and then the OP traced it to some electronic gadget they were carrying in the car, under one of the seats, no part of the car itself.
     
    #2 ChapmanF, Nov 24, 2025 at 8:32 AM
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  3. Tombukt2

    Tombukt2 Senior Member

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    St be getting ready to do you're plan as typed . It's ecmxit time buddy. You want to exit while the vehicle has some value I would imagine . Trade in something . When it's no longer running starting it pretty much worthless.
     
    #3 Tombukt2, Nov 24, 2025 at 8:42 AM
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  4. ChapmanF

    ChapmanF Senior Member

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    Didn't see anything in the OP that made me think the car won't start or run....
     
    #4 ChapmanF, Nov 24, 2025 at 9:27 AM
  5. eliotb

    eliotb Junior Member

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    Fortunately the noise is at least for now silenced. While driving, I thought the beep was behind me. While parked at home, I thought it was perhaps under the dash in the “which smoke detector is it” mode. It definitely was not under the hood.

    If the little basta….I mean darling rears its ugly head again I’ll try to see if i can narrow it down a bit.

    Thanks.

    Eliot
     
    #5 eliotb, Nov 24, 2025 at 12:52 PM
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