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Thread: LMM a/c control malfunction after full flash?

  1. #1
    Lifetime Member Boost's Avatar
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    Question LMM a/c control malfunction after full flash?

    I am trying to figure out why the temperature control in an '09 LMM was acting up after a full OS flash for a DSP5. I know there are a lot of things we don't know about these controllers like invisible tables and how they commmunicate and work together, but a lot of you know a heck of a lot more than me and I'd greatly appreciate your input. This is exactly what happened:

    - was working perfect, LTZ
    - installed DSP5 switch
    - tried to full flash with V7, failed, full flashed with V8 fine
    - A/C blew hot from driver side despite selecting cold (states that later driver side went cold but a/c control head was malfunctioning)

    Right away I realized that I full flashed an older OS from a truck without dual climate control. Re-(full) flashed with correct OS and a/c seems fine.

    However, why would the ECM affect it??

    My thoughts on onther possibilities were:

    - after both batteries were disconnected, actuator lost position? - but this shouldn't happen
    -the failed flash attempt with V7 confused it. - but I hope not, unlikely to have THAT affect
    - the ECM pins were disturbed / loose from switch install - but I was really careful, done a few before, and I think I would have more serious issues.

    Just curious why the OS in the ECU could affect this? If that was the case.....

    thank you for your time
    '12 Caprice PPV 6.0 L77 - daily transportation
    8.7 @ 84 (1/8 mile) bolt-ons

    '02 Silverado RCSB 5.3 L59 - regularly street driven
    8.2 @ 86 (1/8 mile) stock cam and spray
    8.6 @ 84 (1/8 mile) cam and heads no spray

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  2. #2
    Lifetime Member THEFERMANATOR's Avatar
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    The ECM has alot of control over general bus messages. Most of teh time though the BOSCH controllers are pretty good about working with different OS's, but it still has to be teh right gen OS to make it work.
    1995 GMC 2500 SUBURBAN powered by 01 DURAMAX/ALLISON, little of this, a little of that,
    DIAMONDEYE 4" exhaust, CORSA muffler, AFE stage 1 dry filter, custom tuning by me, KENNEDY single pump and pump rub kit.

  3. #3
    Lifetime Member Boost's Avatar
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    Those are exactly my findings also. Thank a lot for everything Ferm!
    '12 Caprice PPV 6.0 L77 - daily transportation
    8.7 @ 84 (1/8 mile) bolt-ons

    '02 Silverado RCSB 5.3 L59 - regularly street driven
    8.2 @ 86 (1/8 mile) stock cam and spray
    8.6 @ 84 (1/8 mile) cam and heads no spray

    Our YOUTUBE CHANNEL featuring the Silverado

  4. #4
    Junior Member
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    I had the same thing happen to me on an LB7. Something went wrong while full flashing a customer's truck & I wasn't able to recover the ecm. To help the guy out I let him use the ecm out of my LB7 until I got his right. Mine had dual zone climate control, his didn't.

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