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Thread: Correcting speedo with vss pulses?

  1. #21
    Potential Tuner Fast240Z's Avatar
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    Quote Originally Posted by EC_Tune
    What DTC's are you seeing? If it's ABS related and you have much bigger than stock tires and/or a gear swap it's simply the ABS system whining that the front and rear sensors are out by > 15%. A Tech 2 can fix that for you.

    And did you enter 40 Pulses per Rev trans output? That's the number that most trucks have.

    If you need to fudge the speedo you can put in the VSS Pulses per Mile that you calculated with the spread sheet.
    The DTC is C0238 ( wheel speed mismatch). Yes on the 40 PPR. the speedo is acurate but still getting the DTC. Do I have to go to the dealer for the tech 2 change?

    Mark
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  2. #22
    Супер Модератор EC_Tune's Avatar
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    Yep. Tech 2 is the only thing that can reprogram your ABS module for the new tire size.
    And you need them to put in a tire size close to the one you have on your truck.

    The other solution is to put in the stock trans rev/mile value and make the speedo VSS Pulse/mile correct. All your shifting will be off as well as the reported speed with VCM Suite but you won't have the dash light (ABS related).
    Last edited by EC_Tune; 02-14-2008 at 03:17 AM.
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  3. #23
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    Attachment 12500 ok heres one of my tunes that i cant adjust the tire size please help my speedometer is going crazy

  4. #24
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    Quote Originally Posted by EC_Tune
    Try this tire calculator.
    I've put a couple hours into it so it should be right for most all tire size applications.

    It's an Excel file renamed to .txt so I could upload it.
    Just save it to your drive and then rename it from .txt to .xls

    Enjoy!

    you sir, are a gentleman and a scholar!!! thank you for your contributions

  5. #25
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    Quote Originally Posted by EC_Tune View Post
    Yep. Tech 2 is the only thing that can reprogram your ABS module for the new tire size.
    And you need them to put in a tire size close to the one you have on your truck.

    The other solution is to put in the stock trans rev/mile value and make the speedo VSS Pulse/mile correct. All your shifting will be off as well as the reported speed with VCM Suite but you won't have the dash light (ABS related).
    Now if I could find a setting in the Tech II for 35in tall tire
    Ellis
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  6. #26
    Advanced Tuner Shrek's Avatar
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    Quote Originally Posted by TwoFast4Lv View Post
    ... Now if I could find a setting in the Tech II for 35in tall tire ...
    Tech 2 will only load a preexisting GM calibration - it will not modify the calibration. Changes to wheel and tires (sometimes a dealership upgrade) require a different calibration - some of these already exist - and are accessible via a VCI number.

    As an example, the same applies to upgrading some newer vehicles to allow Cruise Control to function (which did not originally come equipped with Cruise Control). You call the GM Tech Line (have never found these folks very helpful) and if the calibration exists (i.e. was an option) - they will upgrade the VIN based calibration for your specific vehicle - and issue a VCI number to access this. All for a fee of course.

  7. #27
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    I know this is an old thread, but everything points back to here and I'm not sure if I'm doing this correctly. I made a slight change of tire size, just enough to put me about 2mph out at 60mph (not a big deal, but it bugs me). I went from 255/45r18 to 275/40r18. I used the spreadsheet and you can see the differences. However I'm not sure what all to change.

    Do I just change the VSS tire revs per mile?
    vss.JPG

    Also, I assume I manually scale the transmission as well?
    scale.JPG

    Based off the calculation in the spreadsheet?
    calc.JPG


    Am I missing anything else???
    Last edited by wheezer; 01-02-2014 at 04:33 PM.

  8. #28
    Advanced Tuner 96gt4.6's Avatar
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    I know it's a necro-thread, but here's how I've delt with the dreaded C0238 and the speedo issues with my customers:

    http://www.hptuners.com/forum/showth...The-Fix-Thread
    '17 Whipple'd S550
    Too many other projects to list.....see my YouTube channel for more: https://www.youtube.com/channel/UCr7...-XfDG53sCh6tcw

  9. #29
    Awesome wirte-up! however ive been having an issue because my current tire size is listed as error and the gear ratio at 1 and when I enter the new values the commit button stays ghosted. Ive searched but haven't found anything useful. if I have to manually calculate the revolutions that is ok but just wondering if any one has found a fix.

  10. #30
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    Quote Originally Posted by EC_Tune View Post
    Try this tire calculator.
    I've put a couple hours into it so it should be right for most all tire size applications.

    It's a ZIP file renamed to .txt so I could upload it.
    Just save it to your drive and then rename it from .txt to .zip then unzip it.

    Enjoy!
    I know this is old, but does anyone have this info?
    **Capt. Ron - 7th Dist. Fire**

  11. #31
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    Lightbulb General and easy equation for calculation

    Quote Originally Posted by griswold View Post
    Does anyone know the procedure or proper way to do this. I have an 05 silverado 4x4 with the 4.8l and a 5 speed. When the tune is pulled from the truck, it shows an "error" in current tire size and the size calculator will not pull up. The truck has stock 3.42 gears and I went from a 265/70/17 to a 305/70/17. Any help would be greatly appreciated.

    Jack
    I found an equation for number of pulses this might help you.

    There is an online calculator too.
    Source: https://www.circuitschools.com/pulse...ula-in-detail/