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Thread: 2004 GTO + Flex Fuel Sensor

  1. #1
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    Default 2004 GTO + Flex Fuel Sensor

    Current Setup:
    2004 GTO, Automatic 4L60E, Procharger
    GM LS1B: Service 12586243, HW 12583659
    OS: EFI Live Custom 04110003 upgraded from stock 12587604 (flex fuel disabled)

    I have googled a lot of the different and followed the install on https://ls1tech.com/forums/pcm-diagn...-write-up.html.
    I suspect that I need a different base OS but wanted to verify before going down that conversion.

    (1) Would my current setup be capable of a flex fuel sensor?
    OR
    (2) Find an equivalent custom EFI Live OS tune - Example: an automatic trans version of https://forum.efilive.com/showthread...l=1#post237782.
    OR
    (3) Would I have to flash a stock tune that had flex fuel enabled? Example: 2004 Tahoe, L59 5.3L, PCM 12587603, and then upgrade to EFI Live Custom 04073003.

  2. #2
    Joe (Moderator) joecar's Avatar
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    I see in the COS pdf that 04073003 is compatible with 12587604 (your current setup)...

    I would say you would have to start with a stock tune that had FF enabled ( altho I haven't done any of these )

    If you don't have a 12587604 FF tune, then try starting with a 12587603 FF tune.

  3. #3
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    joecar, Thanks for the reply.
    I did some digging over the weekend and came up with the following.
    Solution: I'm getting an Ethanol Gauge in order to read the ethanol % from the sensor (GM 13577429) and then update the tune as needed after a fill up.

    My goal was to have knowledge of the ethanol % since the E85 can vary drastically in my area (pumps state 51 - 83%).
    The potential negative effects outweighed the benefit of having an integrated Flex Fuel Sensor.
    1. It seemed like the COS had to have FF enabled from the start for it to work. See https://ls1tech.com/forums/pcm-diagn...r-fbody-9.html.

    2. If no COS and still wanted to do a segment swap tune: For OS 603 or 618, I could see where I could get the equivalent of all the functionality and systems on a 04 GTO - DBC, electrical fans, traction control, A/C, etc. And, for my setup I really need the COS for my FI tune.

  4. #4
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    Just save time and check your flex fuel sensor pigtail connection? It is usually broke, dirty or corroded? Just make sure no wires are broke, it is clean, and no corrosion and ut it back together, clear the codes and have a good life!

  5. #5
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    The ECM is perfectly capable of giving you E85 content and even fuel temp and adjust for it.
    "All that is needed for the triumph of evil is that good men do nothing..."

  6. #6
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    @Highlander This was more of finding an EFI Live COS that I could use with the support rather than any hardware issue. From joecar and searching, I would have had to start with a different stock tune that COS 04110003 supports in order to do it. Since this post, I've been updating after a fill up. During Summer months it has been pretty consistent around western PA (Sheetz and Speedway), so I haven't had to update it that much after a fill up. It would be nice to have it work in the loop but since I've it tuned in now, it would be a big lift - something for a rainy day.

  7. #7
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    So.. what seems to be your issue? lack of table location for the flex fuel portion?
    "All that is needed for the triumph of evil is that good men do nothing..."

  8. #8
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    12587603 and 12587604 OSs are not compatible with each other.
    "All that is needed for the triumph of evil is that good men do nothing..."

  9. #9
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    No real issue anymore. For now, I just manually update the tune. If I ever get the time, then I'll take another try at getting a COS 04110003 + 12587604 working solution.

  10. #10
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    Do you have the flex sensor wired up?
    "All that is needed for the triumph of evil is that good men do nothing..."

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