Prius Gen 3 Key not detected SKS System problem?

Discussion in 'Gen 3 Prius Main Forum' started by Dale UK, Oct 9, 2025 at 10:06 AM.

  1. Dale UK

    Dale UK New Member

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    I have a Prius Gen 3 2010 with the Key not detected issue, I only have one key fob, I have changed the fob battery and the 12v accessory battery, the car does not detect the key fob and I have to hold the key to the start button to start the car, every now and then the car will randomly detect the key fob for a short while and then go back to key not detected, I thought it could be a faulty key fob so got a mobile car locksmith technician to come and register a new key fob, he programmed the new fob but could not get it to be picked up by the SKS system he had to hold that Fob to the start button as well, he said that his scan tool told him that there was a fault on the car itself?

    I bought a Techstream interface online that came with Techstream 15 and I successfully connected to the Prius and used the health check utility to scan all of the ECUs, it came back with DTC (B1242 Wireless Doorlock Tuner circuit) and also a DTC for the Nav as well (photo attached), I cleared the codes but the DTC B1242 came back within a few seconds so its picking up a fault somewhere but the Techstream software is not telling me exactly where the fault is which I had hope that it would do and the only reason I bought the interface.?

    I had a flat 12v battery prior to the SKS problem but this was last year and as I already mentioned that once or twice since then the car has randomly detected the Fob and would function correctly for a day or so but its been dead for a few months now and I need to get it working properly again.

    Any assistance greatly appreciated.
     

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  2. Tombukt2

    Tombukt2 Senior Member

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    I don't have the manual set for this car I imagine it'sgoing to lead to a black box in or under dash.
     
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  3. Tombukt2

    Tombukt2 Senior Member

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    Has any of the front doors been in an accident something about the door module talking to test of SKS type system it looks like.
     
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  4. Dale UK

    Dale UK New Member

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    Thanks for the reply, I did have a minor bump on the drivers door before all of the SKS stuff happened, the repair was all done under the insurance they had it for several weeks not sure if they replaced the door panel or just painted it, I will have a look at the report they gave me, I was thinking it had somthing to do with the flat12v battery but yes maybe you are right and it was the minor accident were someone ran into the drivers door, if the SKS system sees a problem with one door will it then just refuse to work at all? do I need to remove the inner door panel to get to the SKS door module?
     
  5. Paul Gregory

    Paul Gregory Senior Member

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    I get the same warning quite often. I just ignore it and it goes away. It's probably bad RFID reception between the fob and the transceiver.
     
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  6. Dale UK

    Dale UK New Member

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    Yes the fault never goes away though its been the best part of a year that it has not been working properly, the Techstream interface gave me the code for the problem as B1242 so for me its an actual fault on the vehicle.
     
  7. hurricos

    hurricos Junior Member

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    In my experience, the fob itself is the problem. I have a fob that'll do this; I discovered one of the buttons had broken. The uC in the fob will not init correctly if it's in a bad initial state when it starts getting power.

    I've also discovered that this fault will not prevent the fob from being used to program another fob correctly -- just has to be good enough to start the car.
     
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  8. Dale UK

    Dale UK New Member

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    Yes I had a mobile car locksmith come to the vehicle, he programmed a brand new key fob for it but that had the same problem, it was he that said his scanner tool said the car itself had a fault.
     
  9. Dale UK

    Dale UK New Member

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    I had a new Key Fob programmed by a Car locksmith he was the one that told me there is a fault on the car because his new fob was also not sensed by the SKS system, you would think that the new key would work properly if its only a problem with the original key fob?