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Thread: TCM COMS w/ HPT

  1. #1


    I have 07 Chevy Avalnche, LS3, 4L80e w/ E38 & T42. Using MPVI pro & latest VCM Scanner release, I only see a few PID's under trans - looks like from manual trans setup. I just checked system with Bosch scan tool and can see normal 4L80e TCM PID's including PC, 1-2, 2-3, etc.. and watch live data. Any ideas? Thanks ahead for any help.
    Last edited by; 10-13-2018 at 02:44 PM.

  2. #2
    Can someone point me to a calibration file w/ 4L80e segment for E38: 12614088? Or tell me how to find one? I tried to find on repository, but ran out of talent...
    Thx ahead.

  3. #3
    Found stock .hpt's for 2007 Avalanche and for 2007 Silverado 2500. Info screen for my current tune and these two stock tunes are below. Any help on the following questions/options would be appreciated:
    1.) All three OS's are E38 2007 - are these compatible to flash to my ECM/TCM (TCM OS is same for both stock files)?
    2.) Can/should I swap 4L80 sector from the Silverado 2500 .hpt into my current .hpt?
    3.) Or should I use compare to copy ECM tune parameters from my current .hpt into Silverado 2500 .hpt and flash this?
    4.) Or should I swap Silverado 2500 4l80 sector into Avalanche .hpt, then use compare to copy current ECM tune into resulting file?
    5.) Do I need to have dealer flash corresponding OS parts into my ECM & TCM, or new ones if this doesn't work?

    Current: OS 12614088
    Stock 2007 Avalanche 1500 5.3L: OS 12605898
    Stock 2007 Silverado 2500 6.0L: OS 12608677
    Silverado 2500.PNG

  4. #4
    Advanced Tuner
    Join Date
    Oct 2013
    The short answer ...

    The easiest course of action for you, would be to get (from your local wrecking yard) a T42 TCM from a 2008 full-size van with a 4L80 (2500 or 3500 series), and install this T42 TCM into your 2007 Avalanche. Depending on the wrecking yard, these T42s may be purchased for as little as $25.

    Then read the ECM and TCM calibrations again from your Avalanche, and tune from there as necessary.

    The long answer ...

    The 4L80 was only offered briefly in 2007 Gen 4 HD trucks, and only in 4x4 models. These quickly transitioned to the 6L90 transmission. Any 2007 Gen 4 HD truck equipped with a 4L80 will use a unique E38 ECM OS (typically 12608677), and T42 TCM OS 24235341. This particular T42 TCM calibration often times will not communicate with other E38 OS.

    Some 2007 trucks had the T42 OS updated to 24239927, which was used universally in 2008 - including HD vans that came equipped with the 4L80 transmission.

    Regarding the 2007 E38 OS numbers you posted ...

    12608677 - was used by 4L80 HD trucks only

    12605898 was updated to 12612291 which was further updated to 12614088

    Also, in the JPEG for OS 12614088, it appears that the VIN has been corrupted, which would mean that the VRAM was likely also corrupted - probably from an inappropriate / incompatible flash using tuning software.

  5. #5
    Thanks for the info/ideas Jon. I talked to salvage yard and they're working on finding a TCM from the 08 van w/ 4L80. Hopefully I can plug in and read it all.

    Alternatively, if I found an 08 1500/2500 Van tune file with VIN, could I have a dealer flash another T42 w/ part# for that van, then change VIN to my truck? If getting the right TCM hardware is a concern, can a dealer get a new/refurb T42 that is correct for the Van VIN?

    On the OS information, I have one question. The stock avalanche file has the same TCM OS as the HD 1500 - both T42: 24235341. Are you thinking that even though my current ECM OS is updated version of the OS in the stock Avalanche tune file, it could be problematic w/ T42: 24235341?

    Last question, is there a reference I can find on the various OS histories?

    Thanks again!

  6. #6
    Advanced Tuner
    Join Date
    Oct 2013
    If your current vehicle uses the same T42 TCM OS as the 2007 HD truck 4L80 does, then you could try swapping in the 4L80 trans calibration and trans diagnostic segments - not sure if HPT will let you do this operation.

    Regarding using a GM dealer. Most will only reprogram a complete vehicle, per its unique VIN. Hard to find any dealer who will bench flash a single controller (your T42) these days.

    GMs calibration database reference the vehicle VIN, and may be found here:

  7. #7
    Ok, I was able to read/write ECM & TCM, have full auto trans calibration pars & diagnostics list in .hpt. But, in scanner, I still do not see TCM... any ideas on this?
    Last edited by; 10-27-2018 at 12:24 PM.

  8. #8
    Senior Tuner
    Join Date
    Feb 2006
    South Carolina
    Quote Originally Posted by View Post
    Ok, I was able to read/write ECM & TCM, have full auto trans calibration pars & diagnostics list in .hpt. But, in scanner, I still do not see TCM... any ideas on this?
    In the Scanner, while connected to the vehicle, select "Vehicle">"Repoll for Supported Parameters" and see if it shows up.

    The scanner only polls for parameters the first time you connect to a vehicle and then works off of the last list to save time on subsequent sessions.

  9. #9
    Thanks ElecTec - I think I tried re-poll, but will do again to be sure.

    Since I was able to read the TCM and looked through the tune, I think I found some issues w/ speedo & shift timing calibration that may explain transmission shift issues. It didn't look like the speedo & shift tables/pars were updates when I switched from 3.73 to 4.10 final drive. I sorted the math and corrected VSS Revs/Mile & PCM Out Pulses per mile. And I used the gear/tire wizard w/ appropriate factor to scale transmission parameters. I haven't got to load & drive it yet, but hopefully this gets me back to previous shift performance at a minimum.

    That would only leave TCM scanning issue to figure out. One thing I am concerned with is that the TCM OS that I read from the vehicle doesn't match the TCM OS in the stock 2007 Avalanche & 2007 Silverado 2500 tune files that I've looked at. I haven't had a chance to research T42:24239927 compatibility to E38:12614088. Is it possible that an OS conflict could only effect scanning but allow read/writes and run ok?

  10. #10
    Closing this out in case it is useful for anyone else down the road:
    >> Purchased T42 TCM from Garrett Tuning w/ OS & Cal loaded per VIN from stock 2007 Silverado 2500-4L80 truck - then VIN changed to my 2007 Avalanche VIN
    >> Installed & did read all ECM & TCM which I am using to work forward from - can read/write and log TCM channels which I couldn't do w/ previous TCM - latest ECM OS rev for the 2500HD and my truck are same, so in good shape on compatibility.