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Thread: T42 TCM read and write

  1. #1
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    Default T42 TCM read and write

    Hi , I have a flashscan v2 and am having comms issues with a faulty t42 tcm . Is it possible to extracts the op system and transfer the data into a purchased second hand unit .

  2. #2
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    T42s are pretty robust, check all wiring and fuses for the transmission circuit. If you want to try a new T42, start with a known good file, change the VIN, and Full Flash a base file.
    ~Erik~
    2013 Sonic RS Manual - 1.4L I4T E78, tuned, turbo mods, etc.
    2008 TrailBlazer SS 3SS AWD Summit White - LS2 E67/T42, bolt ons, suspension, etc.
    2002 Chevy TrailBlazer LT 4X4 Summit White - 4.2L I6 P10, lifted, wheels, etc.

  3. #3
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    Quote Originally Posted by ScarabEpic22 View Post
    T42s are pretty robust, check all wiring and fuses for the transmission circuit. If you want to try a new T42, start with a known good file, change the VIN, and Full Flash a base file.
    Thanks for the reply . I have linked an exchanged unit and now the module shows up present but the issue im having is still present which when acc is on i do see all gear selection on vehicle dash but when engine is running it just
    stays at P even though i can shift and select all gears at shifter . then check trans fault occurs

  4. #4
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    Ok is this a factory vehicle using a factory-matched ECM + TCM calibration? If not, the first visual place you'll see issues is with the gear selector being incorrect.

    If it's a swap, need to make sure the ECM+TCM OS' can talk to each other, GM went through a few variations of CAN comms with the Gen IV controllers.
    ~Erik~
    2013 Sonic RS Manual - 1.4L I4T E78, tuned, turbo mods, etc.
    2008 TrailBlazer SS 3SS AWD Summit White - LS2 E67/T42, bolt ons, suspension, etc.
    2002 Chevy TrailBlazer LT 4X4 Summit White - 4.2L I6 P10, lifted, wheels, etc.

  5. #5
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    Quote Originally Posted by ScarabEpic22 View Post
    Ok is this a factory vehicle using a factory-matched ECM + TCM calibration? If not, the first visual place you'll see issues is with the gear selector being incorrect.

    If it's a swap, need to make sure the ECM+TCM OS' can talk to each other, GM went through a few variations of CAN comms with the Gen IV controllers.
    The TCM has been linked with other modules and correct vin in new TCM has been installed the dealer checked the OS in new TCM and assures all is correct and up to date . He told me that it is an electrical fault
    which may be the neutral start switch or the pressure switch manifold in the trans (4l80e) vehicle is a HSV GTO coupe VZ LS2 .

  6. #6
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    I don't know about the HSV VZ, but the GTO never came with the 4L80E in the US. You have to use a non-factory TCM OS to make it run a 4L80E OR change the wiring with an adapter harness. I doubt a dealership would put the correct 4L80E OS into the TCM as it isn't a factory combo, but we need to check.

    Post the ECM and TCM tunes here along with a full specs of your car. I'm thinking you need to change the TCM OS to work with your 4L80E, if you try to run a 4L60/65/70E TCM OS on a 4L80/85E transmission it usually won't work and will definitely be in limp mode.

    Also not sure what year we're talking, guessing 05 or 06. For 06, the TCM OS is 24235341 and the same as a 07 Suburban which came with the 4L80E.
    Last edited by ScarabEpic22; March 15th, 2021 at 02:26 PM.
    ~Erik~
    2013 Sonic RS Manual - 1.4L I4T E78, tuned, turbo mods, etc.
    2008 TrailBlazer SS 3SS AWD Summit White - LS2 E67/T42, bolt ons, suspension, etc.
    2002 Chevy TrailBlazer LT 4X4 Summit White - 4.2L I6 P10, lifted, wheels, etc.

  7. #7
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    Quote Originally Posted by ScarabEpic22 View Post
    I don't know about the HSV VZ, but the GTO never came with the 4L80E in the US. You have to use a non-factory TCM OS to make it run a 4L80E OR change the wiring with an adapter harness. I doubt a dealership would put the correct 4L80E OS into the TCM as it isn't a factory combo, but we need to check.

    Post the ECM and TCM tunes here along with a full specs of your car. I'm thinking you need to change the TCM OS to work with your 4L80E, if you try to run a 4L60/65/70E TCM OS on a 4L80/85E transmission it usually won't work and will definitely be in limp mode.

    Also not sure what year we're talking, guessing 05 or 06. For 06, the TCM OS is 24235341 and the same as a 07 Suburban which came with the 4L80E.
    sorry , my combo has been running good for about six years , it is an 05 model which we were running the t42 tcm with a PCS controller pigy backed of the original TCM to run the 4l80E . The original TCM is shot so i have no way of extracting info
    from it as when i module check it says not present so i have had the dealer re link another unit in which he has put the Os for that particular vin from vehicle .

  8. #8
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    Quote Originally Posted by Mr teabags View Post
    sorry , my combo has been running good for about six years , it is an 05 model which we were running the t42 tcm with a PCS controller pigy backed of the original TCM to run the 4l80E . The original TCM is shot so i have no way of extracting info
    from it as when i module check it says not present so i have had the dealer re link another unit in which he has put the Os for that particular vin from vehicle .
    Thank you, this information would have been helpful to know initially.

    If you want to keep this setup, check with PCS as to what TCM OS works with their controller and use that. If you are unable to connect to the T42 with EFILive, my guess is there's a wiring issue and/or the PCS controller is causing issues.
    ~Erik~
    2013 Sonic RS Manual - 1.4L I4T E78, tuned, turbo mods, etc.
    2008 TrailBlazer SS 3SS AWD Summit White - LS2 E67/T42, bolt ons, suspension, etc.
    2002 Chevy TrailBlazer LT 4X4 Summit White - 4.2L I6 P10, lifted, wheels, etc.

  9. #9
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    Thank you all, very helpful information!
    Last edited by NicolaOgden; March 20th, 2021 at 07:10 PM.

  10. #10
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    Quote Originally Posted by ScarabEpic22 View Post
    Thank you, this information would have been helpful to know initially.

    If you want to keep this setup, check with PCS as to what TCM OS works with their controller and use that. If you are unable to connect to the T42 with EFILive, my guess is there's a wiring issue and/or the PCS controller is causing issues.
    sorry for mis information . the codes i am getting are from engine on an then P will stay on dash until codes cleared .Click image for larger version. 

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ID:	23722T42 warhawk op system from shacks.ctz


    T42 warhawk op system from shacks.ctz

    this is what i could extract from damaged tc
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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