2004 Prius thinks key fob is in ignition; kills battery

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Laman012, Mar 10, 2025 at 2:48 AM.

  1. Laman012

    Laman012 Junior Member

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    I have a 2004 prius with a regular (non-smart) key system that requires the fob to be inserted into the slot to start the car.

    I have recently changed the 12v auxiliary battery with a new Duralast AGM aftermarket battery. It tests good and holds a charge when fully charged.

    When I turn off the car and open the driver side door before removing the fob, the car will beep to let me know that the fob is still in the ignition.

    Sometimes, after removing the fob, the beeping will still occur, even when there is no fob in the slot.

    When this happens, and I close the door, the battery will invariably be slowly drained and the car won't start without a jump the next morning.

    I've seen quite a few posts on here discussing this problem and every answer is "change the 12v," but in my case, I did 3 months ago, and I'm still having this issue.

    Is this caused by an electrical issues whereby the car can't accurately detect when the key fob is taken out?

    Any advice would be appreciated.

    Thank you!
     
    #1 Laman012, Mar 10, 2025 at 2:48 AM
  2. dolj

    dolj Senior Member

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    Are you having trouble with your dash not coming on when you turn the car on?
     
    #2 dolj, Mar 10, 2025 at 4:50 AM
    JC91006 likes this.
  3. JC91006

    JC91006 Senior Member

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    You may have a problem with your combination meter, where the dash lights will not come on at times. When this occurs, it's often hard to shut off the car, and it's possible the car will have certain dash lights/MFD screen still on when you step away.
     
    #3 JC91006, Mar 10, 2025 at 10:32 AM
  4. Laman012

    Laman012 Junior Member

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    No problems with dash at all.
     
    #4 Laman012, Mar 10, 2025 at 10:45 AM
  5. Tombukt2

    Tombukt2 Senior Member

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    So let me ask you this when this happens if you were to reslot the remote and then pull it out does the beeping now stop? If yes pull the under panel that contains the slot and the dimmer and remove the amplifier which is what the slot is called read the bottom label and take one from another car I have a bunch of them here and stick it in there and plug it in don't mount it to the panel and ride around the block and now try it again did that solve your problem there you go I had this on one car already I changed that amplifier slot device and the problem immediately stopped I don't know if there's an antenna in this thing or how the amplifier actually works or any of that but that fixed the problem in this particular instance which was similar to yours in the car with a black backed remote I would deslat the remote open the door it would still be telling me something at the time I didn't know what it was One day while the door was open and the car was beeping at me I just stuck the remote back in the slot and it stopped and I pulled it out and it stayed off and I closed the door I never lost a battery from this at all. And after that happened the next morning I took the slot amplifier out of a 2005 and stuck it in the car and question which I think is an '07 and that was finished
     
    #5 Tombukt2, Mar 10, 2025 at 10:58 AM
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