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Fob wouldn't unlock car, had to drive with alarm blaring!

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by SquareWheels, Sep 2, 2015.

  1. SquareWheels

    SquareWheels "15kW or stealth" driver

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    Hi all. Yesterday I parked my 2004 UK Prius (without SKS) for about 1 minute having just driven it for 40 minutes, and locked it using the buttons on the fob in the usual way.

    Realising almost immediately that I'd parked in the wrong car-park (!) at Sainsburys I returned to it but the fob wouldn't unlock the car. Nada. The red light still worked on the fob, but wouldn't unlock the car. In the end I used the metal key to open the driver's door, triggering the alarm which I then could not cancel.

    In the end I put the fob *almost* into the slot to start the car, then removed the fob so I had access to its buttons. Still nothing. So I had to drive away with the alarm sounding (how embarrassing!), and with the fob in my lap. When I'd gone about 50yds away, finally the unlock button cancelled the alarm.

    The 12V battery is over 6yrs old but (I just tested it) gives 12.0V no-load, 11.5V with headlights and window-winder together. I've not had this problem before nor have been able to make it fail again since.

    Any thoughts?
     
    #1 SquareWheels, Sep 2, 2015
  2. Beachbummm

    Beachbummm Senior Member

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    6 years old is antique for the battery,i go through one about every 3 years in the florida heat..11.5 is bad, needs to be replaced, on most cars you can insert the metal key into the drivers side door lock turn to the left than back to center to disable the alarm before opening the door, not sure if it works on Toyota..i think no load should read over 12.6 to be considered good
     
    #2 Beachbummm, Sep 2, 2015
  3. kinglew

    kinglew Member

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    New battery need 12 volt low voltage replace
     
    #3 kinglew, Sep 2, 2015
    Mendel Leisk likes this.
  4. edthefox5

    edthefox5 Senior Member

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    12 battery is bad. Also the fob battery is probably bad too.

    The car is throwing a red triangle also I bet upon boot up. It only shows for a second on the dash upon boot. Its pretty noticeable as its not part of the dash bulb check routine. Mine started throwing it at 11.2. Its the only notice you get the battery is about to ruin your day.

    Change both asap at your convenience before it leaves you stranded and then exposes you to the dreaded jumper cables. Many a poster here has destroyed there Prius with bad jumper cable experience.

    If you ever have to jump make sure the donor car engine is off.
     
    #4 edthefox5, Sep 2, 2015
  5. SquareWheels

    SquareWheels "15kW or stealth" driver

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    I just checked. No red triangle upon bootup, no. Maybe the battery isn't quite bad enough yet to trigger that?

    I realise 6.5yrs is getting ancient for a 12V Prius Aux battery, so I should put it on the do-to list. :)

    It's just that the symptoms seemed strange because everything had been fine as I'd been driving the car for 40 minutes up to literally 1 minute earlier. I wondered if there was a car-thief sat nearby with an RF jammer, trying to cause people to leave their cars unlocked?
     
    #5 SquareWheels, Sep 2, 2015
  6. edthefox5

    edthefox5 Senior Member

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    The thing about these little agm's is they fail rather fast. Especially if old. I got exactly 6 years out of my oem battery and that was with loving care with periodic battery tenders.

    And yes you may not be hitting that 11.2 level yet but you will soon. Change that battery out asap...anything to avoid the jump start. It can ruin your car and you'll kick yourself.
     
    #6 edthefox5, Sep 2, 2015
  7. Mendel Leisk

    Mendel Leisk EGR Fanatic

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    12.0 volts at rest is very low.
     
    #7 Mendel Leisk, Sep 2, 2015
    edthefox5 likes this.
  8. SquareWheels

    SquareWheels "15kW or stealth" driver

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    Thanks guys!
     
    #8 SquareWheels, Sep 3, 2015
  9. Firefly1985

    Firefly1985 New Member

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    Just lent our 2004 to a friend and their dog chewed our only fob. How do you drive the car without a fob!?
     
    #9 Firefly1985, Oct 3, 2021
  10. edthefox5

    edthefox5 Senior Member

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    #10 edthefox5, Oct 3, 2021
  11. dolj

    dolj Senior Member

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    You don't. Well, not quiet.

    If the fob is not too badly deformed and still fits in the slot, it should still allow you to start the car and drive it. You can use the physical key that slots into the fob to manually lock and unlock the car.
     
    #11 dolj, Oct 4, 2021
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