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Thread: Last ditch...ANY way to support flex fuel on 2002 COS

  1. #1
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    Default Last ditch...ANY way to support flex fuel on 2002 COS

    I really want to run the ethanol sensor and have the PCM control fueling based on composition.

    I see posts here and there about people running hacked tunes to get this done and I am specifically referring to using a COS (I am boosted). OS for the 2002 Tahoe L59.

    Only other options are to repin to an 03+ pcm

    or

    HPtuners.

    And I don't want to do either of those.

  2. #2
    Lifetime Member GMPX's Avatar
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    GM released one 'real' Flex Fuel OS for the 512K PCM (which is what your 2002) is, problem is it is about 99% full so there is no space for custom OS additions. We didn't support every 2003+ PCM OS for a custom OS conversion, just because of the amount of work involved for each one, again they did do some specific OS's for Flex Fuel in 2003+ but I can't recall if there is a COS for them.
    Not sure how HPTuners is going to help you either unless they have a COS for the 512K PCM running the factory Flex Fuel OS.
    I no longer monitor the forum, please either post your question or create a support ticket.

  3. #3
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    Thanks for the reply. At least know I know why there is no COS for that OS. I was always under the assumption it was just wasn't done and there was no care to do it, rather than an actual hard limit on the PCM.

    To my knowledge, HPTuners does have a COS that allows for real flex fuel on 2002.

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    You don't need to repin for the 1mb PCM. Just delete codes P0135 and P0155 for the O2 heaters and change your red connector plastics to green. Find a 1mb calibration you want to start with and have fun.

    Jeff
    98 GMC RCSB 2WD, Internally stock 305 w/Twin T-3 junkyard Turbos,4L80e,Ramjet intake,42lb.inj., 0411PCM, COS3,4675LBS w/me in it. Best Time on 5 passes-13.01@110

  5. #5
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    Quote Originally Posted by Lextech View Post
    You don't need to repin for the 1mb PCM. Just delete codes P0135 and P0155 for the O2 heaters and change your red connector plastics to green. Find a 1mb calibration you want to start with and have fun.

    Jeff
    when doing this, does the heaters not function? what are the differences?

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    Quote Originally Posted by RADustin View Post
    When doing this, do the heaters not function? What are the differences?
    The heaters still function. On "Most" of the earlier trucks the heaters get their ground/low reference from the harness to a ground point and not back to the PCM.

    Jeff
    98 GMC RCSB 2WD, Internally stock 305 w/Twin T-3 junkyard Turbos,4L80e,Ramjet intake,42lb.inj., 0411PCM, COS3,4675LBS w/me in it. Best Time on 5 passes-13.01@110

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    so the 1mb wants to supply the low reference where the 512K just uses the harness.

    That's neat. I didn't realize it was so easy to swap to 1mb.

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    Remember if you want to run DBW then you will need the matching 1mb DBW components. If you are DBC then you will need a 1mb PCM that has the IAC drivers in it.

    Jeff
    98 GMC RCSB 2WD, Internally stock 305 w/Twin T-3 junkyard Turbos,4L80e,Ramjet intake,42lb.inj., 0411PCM, COS3,4675LBS w/me in it. Best Time on 5 passes-13.01@110

  9. #9
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    If I wanted to go backwards from 1mb to 512 so that I had a COS3/5 available...and I was DBW, I would need to change throttle body or just pedal and tac? Canbus wouldn't matter as this would be in a swapped vehicle.

  10. #10
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    The 2002 T/B is not compatible with the 1mb PCMs. There may be a guru somewhere who can make it work but as far as I know---It won't.

    Jeff
    98 GMC RCSB 2WD, Internally stock 305 w/Twin T-3 junkyard Turbos,4L80e,Ramjet intake,42lb.inj., 0411PCM, COS3,4675LBS w/me in it. Best Time on 5 passes-13.01@110

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