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Thread: Allison A46 New TCM Flash

  1. #1
    New Member
    Join Date
    Aug 2021

    Default Allison A46 New TCM Flash

    I currently have an A40 installed in my 07 LBZ. Previous owner of the truck had purchased a new TCM he intended to send off for tuning and included it with the truck. New TCM is an A46 P/N 24256864. I connected it to the truck and when you use the auto detect function in V8, the TCM does not show. However, if you right click and select A40, it will connect and read out the TCM and shows the TCM has a base file installed. I updated the vin in the new TCM and cal flashed it, but it is still not communicating with the truck. P0602 code shows up saying the TCM is not programed. What am I missing? How do you prepare the TCM using EFILive? I do have my original A40 stock file, but I assume since the OS is different it will not simply flash over.

    Thank you in advance!

  2. #2
    Lifetime Member
    Join Date
    Jan 2006


    You can't put a A40 OS in a A46 or it will brick it, the A46 has different hardware even though the unit looks the same. The safest way to flash a new one is through TIS generally because they take specific OS's from questions/answers in the TIS program and don't cross over to the A40 OS. After flashed with TIS to get the correct OS for the hardware you can then do Cal editing after reading out the new OS.

    Hope this helps.
    Last edited by rcr1978; August 13th, 2021 at 12:27 AM.
    04 LB7
    2010 LMM
    2015 LML

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