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Thread: Possible Allison bug in 139?

  1. #1
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    Default Possible Allison bug in 139?

    Possible Allison bug?

    Flashed a tune in my AL5 (which has been perfectly successful many time before) that I made a few minor TCC release/apply speed adjustments to and now I have no TCC function when in tow/haul and I can't figure out why, didn't even make any adjustments to any T/H tables. After discovering I had no TCC function, as a test I reflashed the last perfectly working tune back in and still have no TCC operation in T/H?

    It had been a while since the last flash on the trans and between those points I updated from build 133 to the current build 139. Could it be a bug in the build 139?

    Should I try a full flash? Never had to do that on this trans before but I'm not sure what to do next.

    I'm including the tunes. First one is the one I ran for over a year that worked fine. Second one is the one I flashed in with the current 139 build that'ss caused the TCC issue and I also included the stock tune just in case someone wants to compare the two previous tunes with the stock one.
    Attached Files Attached Files

  2. #2
    Joe (Moderator) joecar's Avatar
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    Hi BM,

    Try with latest software/firmware: March-05-2011-release-candidate-2

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    Excellent Joe and quite honestly I don't know why I didn't think to do so. I'll give it a go and post back with an update. Thank you.

  4. #4
    Joe (Moderator) joecar's Avatar
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    Mike, if it still fails with the latest software, I'll notify Paul.

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    It's still a no go Joe. Updated to build 155 and updated firmware to the requested 2.07.07 and flashed the last known good tune in (marked as "current" in the tunes I posted above) and still have no TCC function what so ever in tow/haul. It still works perfect in normal mode though and have no DTC codes of any kind. In fact if you wasn't aware the TC is supposed to apply in 2nd thru 5th in tow/haul you'd never even know there was anything amiss, everything else works fine as it always has.

  6. #6
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    Flash the stock tune back in and see if it comes back, sometimes tune files can get corrupted and starting from scratch eliminates some weird 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.

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    That's the next move I was planning unless a different/better idea was recommended first. I also plan to use the original tune file that I have backed up on a flash drive just in case a possible file corruption was caused by an issue with those I store on the laptop itself (BTW, anyone ever have that happen?)

    And thanks a bunch guys. I'l post an update as soon as I have one.

  8. #8
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    Tried a known previous good trans tune (stored on an external drive from a year ago) and also tried flashing with the high speed unchecked this time although that was never an issue, and still no improvement. I'm at a loss at this point but I think if I could revert to a previous build it would be back to normal. IIRC build 133 was the one that always worked fine. Never had the issue until the build 139 update and the current 155 release hasn't resolved it.

  9. #9
    Forum tyhee Site Admin GMPX's Avatar
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    Big Mike, I downloaded your previous working modified tune and the one that is causing you problems.
    The only changes I see in the tune (viewing the files in a Hex editor, not EFILive) appear to be the TCC tables you have changed, which means it's not the software making some random change to some other calibration. Don't bother with a full flash, it won't make any difference. But I am also at a loss to explain why the TCM is doing what it's doing even after you put the other 'working' tune back in.
    The other thing is, a flash either takes 100% or it doesn't, there is many checks done before the TCM (or ECM) can run as normal, if the tune did not flash properly (even one little bit of data wrong) the trans would be in limp mode.
    Perhaps it might be time to check current (if any) DTC's, that might point you to the problem.


  10. #10
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    Thank you for looking. I have been watching for any DTC's but I've yet to have any either before or after any flashes or test drives to date and as I mentioned before everything works perfectly other than the lack of TC in T/H. It operates just as it should in normal mode so I have no reasons to indicate an issue with the trans itself. That's why I'm lost. The only things I have left to try is a full flash (which you now stated won't help) or try disconnecting the batteries for the heck of it or try an older build.

    Can I back up to build 133 if someone has it to share? I know it's not listed on the download page any more. I have a second laptop so I can keep it separate from the current build but what about the firmware in the V2?

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