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False "key left in slot" warning leads to battery drain

Discussion in 'Gen 2 Prius Main Forum' started by pgaryu, Dec 9, 2010.

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  1. pgaryu

    pgaryu Junior Member

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    One day, I drove my Prius with my key fob in pocket. Parked the car. Turned off the power. Opened the driver side door to get off. Heard the continuous beep of "key fob in the slot" warning. I had never heard of it so I did not what it was. Tried closing / opening the door several times. The warning kept coming when I opened it. Tried getting off the car, pushed the lock button. It locked with lock beep normally.

    After a few hours, I found the battery was dead. Had it jump started and the problem had not come back for a few weeks.

    The next time I heard the beeping again, tried many things and found out it's the false warning. I also found it could go away by putting the fob in and out a few times to the slot. Something must be wrong with the key fob detection. Went to dealership with 60k miles check up and told the service manager about this but it happens rarely and he just told me they could not reproduce the issue.

    For today, I did not have any issues when I got off from the car this morning. When I wanted to get in the car again, I opened the door and heard the warning. Tried to start with praying... didn't start. Tried to jump start, but did not successful.

    Now my Prii is in the parking lot of my company. It is intermittent, but I guess it started after I had the key code reprogrammed by the dealer (I lost a key and got a replacement).

    Any idea what to do? Anybody experienced the same thing?

    Thanks for your advice!
     
    #1 pgaryu, Dec 9, 2010
  2. qbee42

    qbee42 My other car is a boat

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    When was the last time that you replaced the battery in your key fob?

    Tom
     
    #2 qbee42, Dec 9, 2010
  3. pgaryu

    pgaryu Junior Member

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    A couple of years ago. I can still lock / unlock the car remotely with certain distance, and I see the small red LED flashes when I pull out the key from the slot, so I do not think it's a battery issue.

    Even if my key battery is dying, I do not think it can cause the false warning I have... is there anybody who get the warning because of the key battery?
     
    #3 pgaryu, Dec 9, 2010
  4. qbee42

    qbee42 My other car is a boat

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    How about your 12V battery? When was that replaced?

    Given what you have said, I am suspicious that a dieing 12V battery is causing the key issue, not the other way around.

    Tom
     
    #4 qbee42, Dec 9, 2010
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  5. pgaryu

    pgaryu Junior Member

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    It's been 6 years for the 12V battery. Yes it's almost the time to replace it.

    However I do not know how the weak battery can cause the warning. How does is cause the alarm?

    And when I had 60k miles check up with the dealer, they told me the battery was getting weaker but still ok.
     
    #5 pgaryu, Dec 9, 2010
  6. BAllanJ

    BAllanJ Active Member

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    Your 12v battery isn't supplying 12v anymore... so whenever the dc dc converter isn't on, the computer isn't getting enough voltage to think properly.. your computer is going to be stoned stupid until you give it a new battery.
     
    #6 BAllanJ, Dec 9, 2010
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  7. qbee42

    qbee42 My other car is a boat

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    Six years is *way* too old for a Prius 12V battery. We can't say for certain that this is your problem, but weak 12V batteries have been known to cause all sorts of freakish problems with the Prius. It's the first place to start when bizarre gremlins show up, especially with a battery as old as yours.

    Tom
     
    #7 qbee42, Dec 9, 2010
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  8. richard schumacher

    richard schumacher shortbus driver

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    #8 richard schumacher, Dec 10, 2010
    1 person likes this.
  9. pgaryu

    pgaryu Junior Member

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    I got a call from the dealership telling me the problem was the battery as many of you mentioned above. Thanks a lot!

    I am not happy with the fact that the dealer could not point it out when I let them do the 60K maintenance with mentioning this false warning issue and paid more than $300. Probably they did not do anything with it... probably the major maintenance was not the right idea as it cannot prevent the obvious trouble for power users.
     
    #9 pgaryu, Dec 15, 2010
  10. richard schumacher

    richard schumacher shortbus driver

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    Never invoke malice when ignorance suffices :_> Dealers often use a pass/fail tester whose default settings can give a false-pass result for a Prius battery.
     
    #10 richard schumacher, Dec 15, 2010
  11. Terry Olson

    Terry Olson New Member

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    My 2006 Prius has done this to me twice. I've had to call my road plan and have them jump the car to start it. I noticed when I opened the door today, there was a beeping as if the key FOB was in the power slot. It wasn't. I inserted the FOB, and the car would do nothing when I hit the power button. So I'm assuming the battery is drained, and am waiting on the Towing Service to jump it. I would love to find out how to stop this!
     
    #11 Terry Olson, Nov 1, 2012
  12. cwerdna

    cwerdna Senior Member

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    Your 12 volt likely needs to be replaced due to old age.

    You can run the test at Weird stuff happening? MPGs dropping? Test The Battery | PriusChat after the car has sat for many hours or overnight. Tell us the 3 voltage values. It's likely toast. I replaced mine on my 06 over a year ago.
     
    #12 cwerdna, Nov 1, 2012
  13. barbie.gee

    barbie.gee Junior Member

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    And what if the 12V battery is new, having been replaced only 6 months ago? I ask because I'm having exactly this problem.
     
    #13 barbie.gee, Nov 13, 2012
  14. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Just because the battery is new, does not mean that it is fully-charged. I suggest you try charging the battery now.
     
    #14 Patrick Wong, Nov 13, 2012
  15. barbie.gee

    barbie.gee Junior Member

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    I'm working on it. Quite a pain to get to the battery when the hatch has to be opened from the inside! :)
    Now, if only I had a battery charger!
     
    #15 barbie.gee, Nov 13, 2012
  16. PriusGuy32

    PriusGuy32 Prius Driver Extraordinaire

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    You can recharge the 12v battery from under the hood at the jump start points! You dont have to hook it up direct to the battery in the trunk.
     
    #16 PriusGuy32, Nov 13, 2012
  17. dorunron

    dorunron Senior Member

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    I concur with PriusGuy32. You can most definitely recharge the 12V battery without having to open the back hatch. Simply raise the hood, remove the fuse panel cover, swing up the red cover. Then connect your charger by attaching the positive cable to the jump start point (under the red cover) and attach the negative cable to a good ground on the body. I usually use one of the strut nuts to clip the negative clip on.

    Set your charger to charge at 4 Amps (Maximum) and also set it to AGM. If you have the "Optima Yellow Top" battery, you can safely charge at 8 Amps. The Optima is also a AGM type battery.

    Ron
     
    #17 dorunron, Nov 13, 2012
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  18. PriusGuy32

    PriusGuy32 Prius Driver Extraordinaire

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    I'd try and charge it overnight at the correct amperage, and if the resting volts arent any better two days later, return it under warranty and get a new battery.

    In my experience, have the auto parts store test the battery before you buy it; the longer a battery sits around (and the Prius battery isnt one that moves off shelves quickly), the more sulfated it can be and not hold a proper charge.
     
    #18 PriusGuy32, Nov 13, 2012
  19. PriusGuy32

    PriusGuy32 Prius Driver Extraordinaire

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    Wal-mart sells a Schumacher smart charger. I bought one 4-5 years ago and love it. It can be used on most anything but comes in handy with the Prius because it has a 2 amp OR 8 amp slow charge (you can also select what type of battery):
    Schumacher Speed Charge 12-Amp Battery Charger - Walmart.com
     
    #19 PriusGuy32, Nov 13, 2012
  20. barbie.gee

    barbie.gee Junior Member

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    Oh! This is great news. The battery is an Exide FP-AGM51JIS.
    Do we have an FAQ on how to do this kind of a charge, with pictures? (I'll do a search, but if someone has it handy... :)) I did already get into the back of the car, and have disconnected the cables from the battery terminals, so I could charge from either...
     
    #20 barbie.gee, Nov 13, 2012
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