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Thread: CVN's Explained.

  1. #1
    Forum tyhee Site Admin GMPX's Avatar
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    Exclamation CVN's Explained.

    Hi All,

    Something we are asked about quite often is to do with CVN's. What are they? What do they do? So I thought I would do a quick explanation. Scattered throughout this forum is various discussions on it, so it was time to summarise in to one thread.

    Q - What is a CVN?
    A - CVN stands for "Calibration Verification Number", this is a fancy name for checksum. What the ECM (or TCM) does is add up all the numbers within each segment of the flash memory, the total of those numbers is what the CVN equals. This allows people with a TechII to quicky check the data in each segment is correct or unaltered (eg, the CVN matches a known program).
    If any data is altered within the segment then the checksum (CVN) will change or not match what it originally was.

    The CVN can also be used by tuners to uniquely identify their own calibrations without needing to read out the ECM / TCM.
    EFILive allows workshops (or stream owners) to modify the CVN to whatever value they desire.
    As an example, a stock E38 CVN list might be as follows -
    Code:
    Segment Name       Part Number CVN
    Operating System   12612381    50D6
    Engine Operation   92200744    26BA
    Engine Diagnostics 92200743    0B9F
    Fuel System        92196978    D0EB
    System             92200742    16E2
    Speedometer        92196106    C405
    A tuner might wish to change each CVN to a pattern they can quickly recognise -
    Code:
    Segment Name       Part Number CVN
    Operating System   12612381    AAAA
    Engine Operation   92200744    BBBB
    Engine Diagnostics 92200743    CCCC
    Fuel System        92196978    DDDD
    System             92200742    EEEE
    Speedometer        92196106    FFFF
    OR
    Code:
    Segment Name       Part Number CVN
    Operating System   12612381    50D6
    Engine Operation   92200744    1001
    Engine Diagnostics 92200743    1000
    Fuel System        92196978    2004
    System             92200742    1000
    Speedometer        92196106    3000
    In the last example the CVN of the calibration segments could be used to indicate a version of the tune, so Engine Operation v1.001, Fuel System v2.004.

    CVN editing is only available to customers who have the stream enabled for the controller they are trying to correct the CVN on. Anytime the CVN is altered from the stock value the vehicle would no longer meet EPA / CARB emissions regulations. Please keep that in mind if you are thinking of putting in some custom patterns like those above.
    You must be very careful not to alter the CVN's to a value already used by the manufacturer, please see page 99 of the SAE HS-3000 purple book for more on this.

    How to alter the CVN in EFILive -
    Click on the CVN Tab (with a E38,E40,E67,T42 or T43 file loaded and active stream for that controller).
    Click on the CVN value you wish to alter and enter in the new number (using only letters A - F and numbers 0 - 9). Hit enter.
    Then click the 'Update' button and save / reflash the file.

    Many early controllers did not support CVN reporting, it really came to light after about 2006, CVN customisation for the Bosch Diesel ECM is not possible.

    Cheers,
    Ross
    Last edited by GMPX; November 16th, 2008 at 11:52 AM. Reason: Formatted CVN's
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  2. #2

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    Well put, made it easy for the n00bs like me.

    -Nemo
    2004.5 LLY Duramax, Compounds, EFILive, EvolvedMS.com 50" Trac Bars, DDP Injectors, PPE Pump, 4" turbo back exhaust, 6" Chrome Stack,
    ATS Trans w/ Triple Loc.




    Evolved M.S, LLC & SS Diesel Tuning

  3. #3
    Forum tyhee Site Admin GMPX's Avatar
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    Default

    Just trying to reduce Emails for support
    Need official EFILive help, please go here.
    For tuning support please post your questions on this forum (or other auto forums).
    Sorry if I don't respond to your PM, don't take it personal.


  4. #4

    Default

    Haha, yea, sorry about that...

    -Nemo
    2004.5 LLY Duramax, Compounds, EFILive, EvolvedMS.com 50" Trac Bars, DDP Injectors, PPE Pump, 4" turbo back exhaust, 6" Chrome Stack,
    ATS Trans w/ Triple Loc.




    Evolved M.S, LLC & SS Diesel Tuning

  5. #5
    Lifetime Member Chuck CoW's Avatar
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    Default Full flash or cal only flash?

    So, I'm assuming the CVNs that Live displays are the the original "correct" CVN for the original calibrations and do not change as live alters the cals. I would imagine that unless you continue to read the cal multiple times from the pcm, the CVN should always report the original correct CVN??? SO, we can use this for a reference when wanting to put the original CVNs back???

    What would be cool would be the ability to load (after the modified tune is finished) the original cal/bin file as the "alt" calibration and be able to toggle between the 2 CVN fields so as to permit a copy/paste operation making it easier to put the "correct" CVN's back into the pcm....

    My suggestion would be to show the CVNs where Live currently displays them, but also build the CVN parameters into the flowchart/tree on the left of the editor in a RED folder like the throttle response tables so as to permit easy comparison/modification of the CVN.

    I'm assuming you'll need to "full flash" the controller to restore the correct CVN?


    Chuck CoW
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    - CLICK HERE NOW FOR MORE INFORMATION! -

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  6. #6
    Forum tyhee Site Admin GMPX's Avatar
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    Need official EFILive help, please go here.
    For tuning support please post your questions on this forum (or other auto forums).
    Sorry if I don't respond to your PM, don't take it personal.


  7. #7
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    "please see page 99 of the SAE HS-3000 purple book for more on this."

    Where can I find this?
    04 LB7
    2010 LMM
    2015 LML

  8. #8
    Forum tyhee Site Admin GMPX's Avatar
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    Quote Originally Posted by rcr1978 View Post
    "please see page 99 of the SAE HS-3000 purple book for more on this."

    Where can I find this?
    It's a little pricey!
    http://www.sae.org/technical/books/HS-3000/2006

    For copyright reasons I probably can't quote the text, but it's along the lines of if someone other than the manufacturer changes the flash data then a new CVN must be created. Which is exactly what you would be doing by entering in your own CVN.

    Cheers,
    Ross
    Need official EFILive help, please go here.
    For tuning support please post your questions on this forum (or other auto forums).
    Sorry if I don't respond to your PM, don't take it personal.


  9. #9
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    So basicaly if the flash data was changed and the CVN was not or was made the same again a emission law would be violated.
    04 LB7
    2010 LMM
    2015 LML

  10. #10
    Forum tyhee Site Admin GMPX's Avatar
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    Default

    Quote Originally Posted by rcr1978 View Post
    So basicaly if the flash data was changed and the CVN was not or was made the same again a emission law would be violated.
    Correct, if you change something in the tune and then correct the CVN to the factory value that is an emissions violation, of course we could have easily made the software do that but that CVN correction function is not about that.
    I use the analogy that if you buy a gun you choose to shoot at a target, wildlife etc, or you choose to commit a crime with it. Same for this, manual CVN correction has a perfectly legitimate reason to exist, if you choose to use it illegally that is your choice.

    Cheers,
    Ross
    Need official EFILive help, please go here.
    For tuning support please post your questions on this forum (or other auto forums).
    Sorry if I don't respond to your PM, don't take it personal.


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