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Thread: LT1 OBD2 Seed / Key algorithm

  1. #1
    Fuel Injected!
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    LT1 OBD2 Seed / Key algorithm

    Hello everyone!

    I'm writing a program to reflash OBD2 LT1 PCMs and I'm having trouble reverse engineering OBD2 LT1 PCM seed/key algorithm. OBD1 is simple, key is just one's complement od the seed.
    OBD2 is harder, for now I have two known good seed / key pairs:

    Code:
    seed:   key:
    0x3192  0x5B3F
    0x3BBA  0x58B5
    There is a document covering GM's 256 key algos, I've made a program calculating all 256 of them, but there seems to be no algo that has a result matching the above...
    So, either I made mistake converting the data from STGTERM.DAT (I doubt that, I've made a script to change the binary to a code, and the algo for LS1 PCMs works correctly), the author of GM seedkey.doc document made a mistake, or the 96-96 LT1s use different algorithm, not in the 256 list.

    If any of you have known good seed / key pairs from LT1 OBD2, please share, it will help hacking the algo :)
    Attached Files Attached Files
    Last edited by dzidaV8; 03-15-2019 at 09:53 AM.

  2. #2
    Administrator
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    The document contains an incorrect response. I'm not sure if it's for this seed but I'm sure you'll spot it quickly. Here is a thread with more details.

    http://www.gearhead-efi.com/Fuel-Inj...key-algorithms

  3. #3
    Fuel Injected!
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    Poland
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    Thank you very much!

    It is working now :)

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