Newbie: Seeking b2799 code advanced options help

Discussion in 'Gen 2 Prius Audio and Electronics' started by U-E, Sep 21, 2021.

  1. U-E

    U-E New Member

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    Hi all!

    UK based, newly aquired Gen2 Prius owner, bought a troubled one for pittence to fix up over time to use as a shopping cart and spare car. 2009 T4, full history, 1 owner (ex-lease). Non-smart entry and no sat nav/reverse cam.

    I have the b2799 immobilizer error code and non-start (bought it as such). Hoping for a little help on the more advanced options to sort this problem.

    Tried the fob in/out 5 times + door open/close 6 times and one min wait for key clone. No key symbol flashes on the dash.

    Tried pin 4 and 13 obd short for 30 mins with ig on, no change. Red triangle and other lights on, and power button remains orange, no start.

    Possible options I can think of at this stage:
    Get a new master key programmed?
    Or
    A reflash of the relevant ecu to accept a different key code (I read this has been done by a locksmith before, apparantly)?
    Or
    Get a second hand complete ecu and key set and swap the lot over (if that would work)?


    What I can add to the thought pot is (baring in mind I didn't pay a lot for it) there was only one key with it which locks and unlocks remotely no problem. And a spare fob socket (transponder receiver next to power button).

    12v aux battery only a few months old but not charging above 11.5v and just had the HV unit out today with 7.5v down to 6.5v on the cell modules. Makes me think someones hit the issue and used external 12v sources to continually fiddle about to the detriment of the batteries (New aux battery en route and HV unit out for refurb/replacement).

    Ran a stable similar spec 12v battery to read codes etc. Only b2799 showing. Not sure if the low HV charge will cause b2799, but the thought has crossed my mind that it wont help. Car was running fine up until a couple of months ago (when it passed the mot).

    Anyone got a helpful thought on what I can do to get around this problem in an effective way? I know it will cost, which is fine.

    And FYI I have techstream and a 2.0.4 mini vci heading to me as I have a GS450h as well that needs the tpms's sorting. Not sure if that can help with the Prius problem much?

    Thanks!
     
  2. dolj

    dolj Senior Member

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    The B2799 DTC means that the key fob was not in the key slot when the 12 V supply was reconnected to the car. If the key fob was in the slot, then could be that the RFID chip is not present in the key fob. This can happen if someone replace the gutter fob shell and did not move the RFID chip over to the new shell. The RFID chip looks like a rectangular piece of plastic, black in colour, and has one corner cut off along one of the long sides. See the following image.

    Prius Key Fob RFID Chip 2.png

    If it is none of those things, then you will need to dig further.

    If you have multiple warning lights currently in the dash, you most certainly have other DTCs that your current OBDII reader is not picking up. Techstream will be most useful on this Prius as well as your Lexus, for reading any codes present.
     
  3. U-E

    U-E New Member

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    Thanks for the insightful info! Much appreciated reply.

    Just checked and the RFID is in the fob I got with the car. I have techstream but an older lead, only b2799 showing (I wanted the newer firmware lead for 'write' ability for the tpms's on the lexus, hopefully).

    I read somewhere about trying 20 times to start a prius with a key issue causes somekind of lock out (and hence the rwd triangle light maybe)? I wonder if this is what happened. In anycase, its clearly fudged and will need something done - but what is the best option I wonder? (Key recode, ecu reflash or get a complete ecu and key kit etc).
     
  4. dolj

    dolj Senior Member

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    Just to leave no stone unturned, does that also mean that the key fob was or was not in the key slot when the 12 V supply was reconnected to the car?

    Have you cleared the codes with Techstream and see what happens then?

    Have you run a full 'Health Check' in Techstream for codes?
     
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