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Alarm going off randomly

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by winkleman129, Mar 27, 2022.

  1. winkleman129

    winkleman129 New Member

    Joined:
    Mar 27, 2022
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    USA
    Vehicle:
    2007 Prius
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    N/A
    Hey all I've been having an issue with my 07 Prius. The alarm has been going off randomly the past couple days and I've replaced the battery in the fob and replaced the 12v battery in the car and I also did a test with the fob and covered it in tinfoil to make sure the fob wasnt causing the panic and the alarm still went off with it covered. One weird thing did happen when I went to go grab the door handle this last time the car unlocked like 5 times like spam unlocked it was the weirdest thing. Also I have made sure everything is closed as well. I'm now trying to see if the alarm still goes off if the car is unlocked I'm not sure what to do next but any advice is appreciated thanks
     
    #1 winkleman129, Mar 27, 2022
    Last edited: Mar 27, 2022
  2. mr_guy_mann

    mr_guy_mann Senior Member

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    Vehicle:
    2006 Prius
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    Four
    Hello and welcome to PriusChat! So, a likely cause for the alarm system to randomly sound off is a problem with one of the door or tailgate "open" switches (or wiring). A clue to this would be if you ever notice the red "door ajar" light active on the dash when you think everything is closed (my 06 has that happen when the tailgate isn't completely latched).

    Another possibility might be a problem with the driver's door latch- it has switches to monitor the door lock position for power lock operation and the alarm. AFAIK if someone "manually" works the lock while the alarm is armed then it will activate the horn.

    A latch (or wiring) fault could also explain the "rapid fire" unlock operation. The ecu commands unlock but when it moves the switch sends the wrong signal to command lock again- and back and forth.

    It is helpful to have a scantool such as Techstream (Toyota's diagnostic software). Many here get a bootleg copy with a mini VCI cable (interface that connects to the car) from amazon or ebay and install it onto an old windows computer. I think it can read the history of what triggered the last several alarm events.

    Posted via the PriusChat mobile app.
     
    #2 mr_guy_mann, Mar 27, 2022
  3. winkleman129

    winkleman129 New Member

    Joined:
    Mar 27, 2022
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    Location:
    USA
    Vehicle:
    2007 Prius
    Model:
    N/A
    Thanks for the response the car alarm doesn't seem to go off if I keep the car unlocked so far. I'm going to take it to a car electronic specialist tomorrow to see if they can find the issue I'll relay everything and what you said I'll post an update if I find out what the issue was.
     
    #3 winkleman129, Mar 27, 2022
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