no start after wrong fob in key slot

Discussion in 'Gen 2 Prius Main Forum' started by Dale I, Jun 7, 2025 at 5:22 PM.

  1. Tombukt2

    Tombukt2 Senior Member

    Joined:
    Nov 29, 2020
    11,937
    2,109
    0
    Location:
    Durham NC
    Vehicle:
    2009 Prius
    Model:
    Base
    UHS that's the electric key supplier that's selling ex horse dongles that will work and are returnable if not .for about 88 bux you can get all the tools to code grab and redo fobs etc for about 340 you can get self contained tool that can grab clone etc almost any vehicle .
     
  2. Dale I

    Dale I Junior Member

    Joined:
    May 18, 2021
    20
    5
    0
    Location:
    Point Arena,Ca.
    Vehicle:
    2004 Prius
    Model:
    II
    I didn't see any thing that looked like that chip in the old or new case. The only thing was the small, printed circuit board, that I transferred back and forth...
    The new case had worked the previous day...wonders never cease...
    I'll drive around today a bit...
     
  3. ChapmanF

    ChapmanF Senior Member

    Joined:
    Mar 30, 2008
    26,182
    17,136
    0
    Location:
    Indiana, USA
    Vehicle:
    2010 Prius
    Model:
    IV
    Whether you saw it or not, the car can tell the difference between the case that has the right one in it and the case that doesn't.
     
    Tombukt2 likes this.
  4. Dale I

    Dale I Junior Member

    Joined:
    May 18, 2021
    20
    5
    0
    Location:
    Point Arena,Ca.
    Vehicle:
    2004 Prius
    Model:
    II
    but why did it work that day before???
     
  5. Tombukt2

    Tombukt2 Senior Member

    Joined:
    Nov 29, 2020
    11,937
    2,109
    0
    Location:
    Durham NC
    Vehicle:
    2009 Prius
    Model:
    Base
    Wasn't it in old case or old case wasn't thrown out yet on seat floor or such do not know generally would need to be in that amplifier you call a slot .
     
  6. ChapmanF

    ChapmanF Senior Member

    Joined:
    Mar 30, 2008
    26,182
    17,136
    0
    Location:
    Indiana, USA
    Vehicle:
    2010 Prius
    Model:
    IV
    When we diagnose things on PriusChat from hundreds of miles away, sometimes we end up attaching not the same amount of certainty to every observation that gets reported. It's not always the case that something reported has been mistaken, but it has happened plenty of times before.

    There are certain things we do know:

    1. A complete fob has both a circuit board and an RFID chip in the case, and the RFID chip looks like the picture in post #20. This is certain. Many of us on PriusChat know it, and have taken fobs apart and seen it. I've got one right here.
    2. You have posted (repeatedly) that you weren't able to spot the RFID chip in either the old or the new case. That doesn't change what we know about the fobs (see 1.), but it changes what we know about how careful an observer you might be.
    3. You have posted that the car does start with the old fob case, after you "put the guts back in" (and since you keep saying you've never seen the RFID chip, the only guts you can have meant would be the circuit board). But that fob case works in the car, so the correct RFID chip is in it now, and therefore, if you never moved it, never left.
    4. You have posted that the car did start, "that day before", with the new fob case.

    True, the explanation would be difficult if we had to take 4. as a confirmed, certain observation. On the other hand, if anything about 4. is perhaps somehow misremembered, the story becomes a very simple one that has been seen on PriusChat many a time before.
     
    Brian1954 and xw20_driver like this.
  7. xw20_driver

    xw20_driver Junior Member

    Joined:
    Feb 4, 2025
    40
    14
    0
    Location:
    PNW
    Vehicle:
    2007 Prius
    Model:
    II


    Watch this video, skip to around the 4 minute mark. He points out the RFID chip. You might need to carefully pry and pick it out without destroying the shell. This is the chip the car immobilizer is married to. You already confirmed the old fob case starts the car. Just move this tiny chip over to the new case and reassemble. It shouldn't need to be glued down.
     
    Brian1954 likes this.
  8. Dale I

    Dale I Junior Member

    Joined:
    May 18, 2021
    20
    5
    0
    Location:
    Point Arena,Ca.
    Vehicle:
    2004 Prius
    Model:
    II
    Thank you all for your patience.
    RFID chip is now in the new fob and all is well...
     
  9. dolj

    dolj Senior Member

    Joined:
    May 14, 2012
    8,166
    4,161
    0
    Location:
    Wellington, New Zealand
    Vehicle:
    2007 Prius
    Model:
    N/A
    Just to follow up on this point, if the cases you swapped were for an SKS fob and you did not transfer the RFID chip, then you will have no issues until the day the fob battery dies and you need to use the slot. Without the RFID chip and with a dead fob battery, an SKS car will not start with the fob in the slot. You might want to check your work, if that is possible.
     
  10. Dale I

    Dale I Junior Member

    Joined:
    May 18, 2021
    20
    5
    0
    Location:
    Point Arena,Ca.
    Vehicle:
    2004 Prius
    Model:
    II
    Since the original fob is not a SKS and the replacement isn't either...I'm not sure where this is going...once I found the chip, all is well and it was all operator error...
     
  11. dolj

    dolj Senior Member

    Joined:
    May 14, 2012
    8,166
    4,161
    0
    Location:
    Wellington, New Zealand
    Vehicle:
    2007 Prius
    Model:
    N/A
    You said previously that you have changed several key fob cases in the past with no problems. I did make the assumption that one of those might be your SKS '04. Other than that, I don't know what combination of SKS vs non-SKS those fobs might have been. As you did not know of the existence of the RFID chip until now, I also have to make the assumption that all the previous key fobs were SKS ones, otherwise, the claim of having no problems does not make sense.

    A non-SKS fob will not start the car without the RFID chip, whereas an SKS fob will start the car as long as you do not insert it in the slot. Seeing as that mode is the fallback for getting an SKS car started when the fob battery goes flat, I thought it was worth mentioning so the owner's of the cars that relate to the fobs you changed in the past will not be caught out in the event of a flat fob battery.

    That is all I meant.