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What does the Key FOB in the dash do exactly?

Discussion in 'Gen 2 Prius Audio and Electronics' started by JahT, Jun 6, 2022.

  1. JahT

    JahT Member

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    I tried searching around, but does anybody know what putting the Key FOB in the dash does?

    If it is to be done when there is no FOB battery power (or for storage while driving), then does it use near-field RFID to identify the FOB?
    Does there have to be some small amount of power left in the FOB battery or can you take the battery out and have it still work?
    On the left side of the FOB there is a hole where you can see the internal key, does that make metal contact and complete a signal circuit to allow operation?
    Also it feels like it can get locked in there, is there a solenoid lock that locks the key in the dash in some event?
     
    #1 JahT, Jun 6, 2022
  2. ChapmanF

    ChapmanF Senior Member

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    If you take the fob apart, you'll see that in addition to the circuit board for the wireless functions, there is also a little bitty black passive RFID chip. It doesn't need any battery power to work, or electrical connection. The energy in the RFID field transmitted by the in-dash antenna is enough.

    Mostly you hear about that little chip when people buy replacement fob cases, and they move over the wireless circuit board but leave the RFID chip behind in the old case.

    And yes, the slot has a solenoid to discourage you leaving the car with it turned on or unparked.
     
    #2 ChapmanF, Jun 7, 2022
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  3. JahT

    JahT Member

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    Thank you, that confirms what I thought. Does it seem possible that the passive RFID chip could get damaged maybe from dropping keys and maybe then the car won't be able to read the RFID chip.
     
    #3 JahT, Jun 7, 2022
  4. ChapmanF

    ChapmanF Senior Member

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    I haven't heard of it happening, but who am I to say never?
     
    #4 ChapmanF, Jun 7, 2022
  5. Another

    Another Senior Member

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    Did the fob ever get wet?
     
    #5 Another, Jun 8, 2022
  6. Moving Right Along

    Moving Right Along Senior Member

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    In general, passive electronics are more durable than active ones. There’s no current to interrupt and no moving parts to break or misalign. It works just like the RFID tags in credit cards or “Real ID” drivers licenses and passports. The only way to damage them is intentional destruction (like cutting them in half).
     
    #6 Moving Right Along, Jun 8, 2022
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  7. JahT

    JahT Member

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    Good question, I am mostly asking for understanding if it ever locks me out or fails to drive with a dead-battery FOB inserted.

    So for models without SKS, do they still use a FOB but have to insert it in order for the car to start?
     
    #7 JahT, Jun 8, 2022
  8. mmmodem

    mmmodem Senior Taste Tester

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    On the Prius C, the low end model just reverts to a good old fashion key to start the car.
     
    #8 mmmodem, Jun 8, 2022
  9. dolj

    dolj Senior Member

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    A Gen 2 Prius with SKS will use the fob in the key slot as a fallback if the fob battery goes flat, so yes.

    You can also disable the SKS with the 'Key' button under the steering wheel and then the car requires the fob to be inserted into the key slot to start.
     
    #9 dolj, Jun 8, 2022
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