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Prius alarm goes off with no reason

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by william_kang, Jan 27, 2016.

  1. william_kang

    william_kang New Member

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    My Prius alarm goes off with no reason day and night. I did check everything like door and hatch back, they are properly closed and nothing could have caused the alarm to go off. I brought my car for checking but what the mechanic can do is just set the horn off, they couldn't find the cause. Anyone encounters the same problem, please help provide value response.
    Thanks,
    William
     
  2. DRACO

    DRACO Member

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    Welcome aboard.

    Did you do any recent repairs to the door locks and or do they work properly? Sit in the car and use your remote to see if the locks go into lock position when alarm is activated.
     
  3. william_kang

    william_kang New Member

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    Thanks for your comment.
    The door is ok, never repaired, and properly locked. I used to bring my car to mechanics, but they found nothing. They just help me set the horn off, so that when alarm goes off at night it won't disturb neighbors.
     
  4. Paradox

    Paradox Prius Enthusiast / Moderator
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    Moved to the appropriate Gen 2 forum from the Gen 4 forum.

    Now that the Gen 4 forums are on top of the Prius v forums, people run there instead of the v forums to post without looking around.......
     
  5. Bill the Engineer

    Bill the Engineer Senior Member

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    Best way to keep from setting off the alarm accidentally...

    [​IMG]

    Bill the Engineer
     
  6. gerbre

    gerbre Junior Member

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    Maybe William should tell us if he has a Prius gen 4, Prius gen 2. If he has a key fob with an alarm button, then Bill's solution should work.
     
  7. RRxing

    RRxing Senior Member

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    Or tell us if it is an aftermarket alarm system...
     
  8. valde3

    valde3 Senior Member

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    Is this even factory alarm or some aftermarket one? Or is it just panic button on key?

    Especially if it’s some aftermarket one test your 12V battery (you can find instructions online how to test gen 2 Prius 12V battery easy without any tools) Aftermarket alarms are sensitive for 12V battery problems and since Prius can work with pretty bad 12V-battery it could be the reason.
     
  9. william_kang

    william_kang New Member

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    I am not sure whether the alarm is a factory or aftermarket as it is a second hand Prius from US. If it is aftermarket one, what should i do to avoid 12V problem that lead to Alarm goes off?
     
  10. mmmodem

    mmmodem Senior Taste Tester

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    Aftermarket alarms usually have their own siren. Since you mentioned the horn, I'm inclined to think you are pressing the panic button on the fob by accident or it is faulty. Very easy way to test. Take the battery out of one fob and see if it goes off. Repeat for the other fob.
     
  11. xliderider

    xliderider Senior Member

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    OP, have you or someone else changed the fob battery lately?

    The panic button may be stuck, and was caused when reassembling the fob case improperly.
     
    #11 xliderider, Jan 28, 2016
    Last edited: Jan 28, 2016
  12. DRACO

    DRACO Member

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    Post a picture of your remote
     
  13. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Would it be unreasonable for you to disconnect and remove that alarm?
     
  14. Michael Warren

    Michael Warren Junior Member

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    I don’t care about the 12v battery or key fob. I just have 1 simple question.

    How do I totally disable the factory car alarm and still have normal horn function?
     
  15. Daedalus

    Daedalus New Member

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    I love how nobody answers on this forum, they just keep typing about whatever

    I've been trying to fix this same problem for years, and nobody knows, but nobody days, "I don't know"
     
    #15 Daedalus, Oct 19, 2019
    Last edited by a moderator: Oct 19, 2019
  16. dolj

    dolj Senior Member

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    Generally speaking, people who don't know do not post anything. It would serve no purpose for 20 or 30 people to post "I don't know" posts, except to fill the thread with unnecessary clutter.
     
  17. Prodigyplace

    Prodigyplace Senior Member

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    Perhaps you should ask Danny for your money back since the forum does not provide the expected level of service.
     
  18. pasadena_commut

    pasadena_commut Senior Member

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    One thing to do would be to check that the fobs are not at fault. Taking the battery out would be best, but that's a PITA. So instead try rolling them up in several layers of aluminum foil to block the RF when you get home. Do a positive control - press the alarm key through the foil to verify that the signal is really blocked. If the alarm still goes off at night while they are blocked like that then the fobs are not the problem. If you are "lucky" the alarm will not go off. Then you can see which one is at fault, by wrapping them one at a time. Honestly I doubt this is it, but since this is so easy to do, you should at least rule out the possibility. Also if the alarm only goes off once a week, or something like that, you will have to run this experiment for a very long time.