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Thread: 02 COS3 Invalid Checksum

  1. #1
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    Default 02 COS3 Invalid Checksum

    I am wanting to flash 02020003 OS into a 2002 12200411 PCM with a 6.0, 4L80e calibration.
    I have a V2 and the newest updates. When I try to full flash the 02020003 OS into the PCM I get an error message of Tune File has an incorrect checksum.
    I am not sure what to do next. I have looked through all of the tunes I have saved and I don't have any 2002 Gen3 truck COS3 tunes that I could use as a Full Flash starter tune. Any guidance would be welcome.

    Jeff
    98 GMC RCSB 2WD, Internally stock 305 w/Twin T-3 junkyard Turbos,4L80e,Ramjet intake,42lb.inj., 0411PCM, COS3,4675LBS w/me in it. Best Time on 5 passes-13.01@110

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    I took my V2, Bench Harness and PCM to work and tried to flash the 02020003 OS. I used my work laptop. I got the same error message "Tune File Contains a Bad Checksum". I did have an 02020003 calibration for a 2002 Gen3 truck saved on my work laptop. That COS3 flashed into my PCM just fine. Something seems like it must be wrong with the 02 COS3 calibration that comes with the software as a base calibration.
    I then did a cal flash into my PCM with the tune info I needed---So, I am up and running.

    Jeff
    98 GMC RCSB 2WD, Internally stock 305 w/Twin T-3 junkyard Turbos,4L80e,Ramjet intake,42lb.inj., 0411PCM, COS3,4675LBS w/me in it. Best Time on 5 passes-13.01@110

  3. #3
    Joe (Moderator) joecar's Avatar
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    Hey Jeff, I pm'd Tech Support.

  4. #4
    Lifetime Member GMPX's Avatar
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    Quote Originally Posted by Lextech View Post
    Something seems like it must be wrong with the 02 COS3 calibration that comes with the software as a base calibration.
    The files that come with the software don't have any calibration data in them, they are blank, you need to cal flash something in there after putting the custom OS in.
    I no longer monitor the forum, please either post your question or create a support ticket.

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    That is what I did. I opened V8, Selected the "Tune" Tab, Selected "LS1b" controller, Opened the "Custom OS" Folder, Chose 02020003 and then selected "Full Flash" The dialog/status box opened and scrolled down a few lines and then the message "Tune File Contains a Bad Checksum" popped up and I could go no further. I then found an old COS3 tune I had for another truck that was the same 02020003 OS and Full flashed it into the PCM with no problems. I then did a cal only flash with the initial info I needed. I can't get the 02020003 OS from the Custom OS folder to work.

    Jeff
    98 GMC RCSB 2WD, Internally stock 305 w/Twin T-3 junkyard Turbos,4L80e,Ramjet intake,42lb.inj., 0411PCM, COS3,4675LBS w/me in it. Best Time on 5 passes-13.01@110

  6. #6
    Joe (Moderator) joecar's Avatar
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    Hi Jeff,

    Paul said that V8 fails to ignore the checksum when flashing an empty COS, he is working on an update, V7 should work ok.

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    Thanks Joe,
    I am up and running---No Problem. It just seemed like a software issue that I thought should be brought to your attention.

    Jeff
    98 GMC RCSB 2WD, Internally stock 305 w/Twin T-3 junkyard Turbos,4L80e,Ramjet intake,42lb.inj., 0411PCM, COS3,4675LBS w/me in it. Best Time on 5 passes-13.01@110

  8. #8
    Joe (Moderator) joecar's Avatar
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    Quote Originally Posted by Lextech View Post
    Thanks Joe,
    I am up and running---No Problem. It just seemed like a software issue that I thought should be brought to your attention.

    Jeff
    Yes, thanks, please feel free to bring any software issues up, Paul wants to fix them promptly.

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