Key fob donot work with new battery only with used old one.

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by GG707, Feb 10, 2022.

  1. GG707

    GG707 Member

    Joined:
    Sep 24, 2018
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    Location:
    athens
    Vehicle:
    2009 Prius
    Model:
    Excel
    Hey, I have noticed something strange,

    I got the message key low battery or smt by the car, So i changed the battery and the car did not unlock with the handle, then i tried to unlock the car by pressing the unlock button on the keyfob but it did not unlock too... So i opened the car by the key blade that is in the key fob... then I pressed the brake and pushed the start button but the message key not detected appeared on the dash,

    So i touched the key to the start stop button and started the car... as far my oppinion was that the new battery was not so good maybe it was discharged or smt...

    I checked it with a multimeter so i could confirm that the battery was 3.14v... also i double checked the voltage by the contacts on the keyfob pcb to be sure tha the battery mount contacts are operable so the circuit gets power by the battery... there comes the strange thing...

    i must refer ta this point that when i put back the old battery the keyfob operated as normal i just kept getting the message low key battery ... so

    I tried to measure the voltage during pressing a button and i noticed that with the old used battery the static voltage is 2.97v and when pressing any key (lock or unlock) i get the led lighted and car locks or unlocks as normal but i read 1.96 volts on the key fob until i release the button,

    On the new battery rest voltage is 3.14v but when i press any button the voltage drops to 2.95 but the led donot light and the car donot respond...

    Have someone been in this situation? Is there some idea of why the key donot operate as normal with a new battery??? At this point i should mention that i used a couple of leds to discharge a bit the new battery but it behaves the same way...
     
  2. GG707

    GG707 Member

    Joined:
    Sep 24, 2018
    59
    26
    0
    Location:
    athens
    Vehicle:
    2009 Prius
    Model:
    Excel
    Problem Solved,

    Ignore this it seems that with 2AA batteries in series the key responds properly , so probably the cr1632 batteries i bought where dead... they could not even light a led properly after all...( a simple 3mm led) while the used battery might have lower rest voltage but seems that can provide the proper miliamps neded for the key to trasmit the signals... also i noticed the key led lighting very much so maybe the voltage of 2.6v(that my aa nimh rechargable cells had was more than enought...
     
    ColoradoBoo likes this.
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