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Thread: 6.7 speedo correction help please

  1. #1
    Tuner in Training
    Join Date
    Sep 2015
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    6.7 speedo correction help please

    Hello all!

    I've read though may posts on this topic and tried what i thought to be the correct route.

    2012 f-450

    stock tire size 245/75 17, new tire size 255/70 22.5

    stock file has 655 rev per mile.

    dash reads 60 MPH, GPS reads 68 MPH.

    changed rev per mile from 655 to 578, set use VID to Disable.

    uploaded tune (write calibration to ECM, write entire to TCM).

    Speedo has not changed at all, still the same 8mph offset. Please let me know what i might be missing?

    files attached, stock and modified.

    Thanks in advance, Gerry

  2. #2
    Tuner in Training
    Join Date
    Sep 2015
    Posts
    31
    Anyone?


    Quote Originally Posted by gerry_foster View Post
    Hello all!

    I've read though may posts on this topic and tried what i thought to be the correct route.

    2012 f-450

    stock tire size 245/75 17, new tire size 255/70 22.5

    stock file has 655 rev per mile.

    dash reads 60 MPH, GPS reads 68 MPH.

    changed rev per mile from 655 to 578, set use VID to Disable.

    uploaded tune (write calibration to ECM, write entire to TCM).

    Speedo has not changed at all, still the same 8mph offset. Please let me know what i might be missing?

    files attached, stock and modified.

    Thanks in advance, Gerry

  3. #3
    Tuner in Training
    Join Date
    Sep 2015
    Posts
    31
    Hello Gerry,

    Our Ford engineer has reviewed this. In this particular vehicle, this functionality will not work. In this vehicle the Speedometer is controlled through the BCM which we do not support.

    Chad Stowell
    HP Tuners LLC

    FYI, if you are trying to do this on a 12 powerstroke.

    Looks like the only option is an inline hypertech module....


    Quote Originally Posted by gerry_foster View Post
    Anyone?

  4. #4
    Advanced Tuner JaegerWrenching's Avatar
    Join Date
    Jun 2018
    Location
    Albuquerque New Mexico
    Posts
    465
    You can use Forscan in the later trucks to correct this issue. But there was only so much room for correction before it'd throw a code. I think someone did solve this problem but not 100% sure.

  5. #5
    Senior Tuner Higgs Boson's Avatar
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    Mar 2010
    Location
    Texas Hill Country
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    3,299
    yes, forscan works

  6. #6
    Tuner
    Join Date
    Jul 2011
    Location
    Fort worth, TX
    Posts
    126
    I would love to know how FORScan works because I can’t do anything that doesn’t trip the wrench light on my 15 f250 and it doesn’t matter how many pcm relearns I do. I’ve read threads all over saying you have to use FORScan but not one post showing that it actually worked.
    15 C7Z M7