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Thread: Fuel level ohm range

  1. #1
    Potential Tuner
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    Fuel level ohm range

    Wondering if its possible to adjust the fuel level workable ohm range in my 04 lq9 pcm. I have not yet bought a tuner and an answer to this will likely make the decision for me. I just recently swapped a lq9 out of an 04 Cadillac Escalade into an 86 k5 blazer with a 0-90 ohm sending unit. I need to somehow alter the ohm range being input to the pcm or program the ECM to a 0-90 ohm range. Is that possible? If so it would make things a hell of a lot easier for me. I live in the regulation state of California so this is required to pass our awful smog laws.

  2. #2
    Senior Tuner
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    Download the VCM Suite demo software, it has a selection of sample tune files you can open and look through. But yes, there is a section for Fuel System that covers the gauge/sender config, tank volume, etc.

  3. #3
    Advanced Tuner
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    It is possible to rescale the range in the PCM.
    Do they have to scan the PCM and scan for fuel level?
    What gauges are you using?

  4. #4
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    No gauges at the moment, I will likely end up running a tablet for awhile until I get all the gauges figured out. I just need my pcm to have the correct fuel level for my evap system to work.

  5. #5
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    In your car, the fuel level sensor goes straight on the instrument panel. In Escalade, it goes to the engine control module and then on the instrument panel. It is easier to leave an old sensor 0-95 Ohms just a pcm will not see the amount of gasoline, and you and the dashboard will see

  6. #6
    Advanced Tuner TheMechanic's Avatar
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    26.0 Gallon Tank (Short Bed Pickup and 4-Door Utility)

    E
    40-66 ohms
    1.0 V
    0-13%
    0-11.9 L (0-3.1 gal)

    1/4
    83-110 ohms
    1.25 V
    30-35%
    32.8 L (8.7 gal)

    1/2
    118-140 ohms
    1.6 V
    50-55%
    51.3 L (13.5 gal)

    3/4
    150-190 ohms
    2.2 V
    72-78%
    74.3 L (19.7 gal)

    F
    197-250 ohms
    2.5 V
    88-100%
    92.8-98.4 L (24.5-25.9 gal)

    Low Fuel Indicator On
    62-72 ohms
    1.1 V
    11-17%
    16.5 L (4.3 gal)

    Low Fuel Indicator Off
    74-83 ohms
    1.2 V
    14-25%
    18.9 L (5 gal)

    33.0 Gallon Tank (Suburban 1500 and 2500 Series)

    E
    40-58 ohms
    0.9 V
    0-13%
    0-15.1 L (0-4 gal)

    1/4
    83-110 ohms
    1.25 V
    30-35%
    41.6 L (11 gal)

    1/2
    118-148 ohms
    1.9 V
    50-55%
    64.4 L (17 gal)

    3/4
    155-195 ohms
    2.3 V
    68-78%
    84 L (22.2 gal)

    F
    199-250 ohms
    2.5 V
    88-100%
    118.8-123.4 L (31.4-32.6 gal)

    Low Fuel Indicator On
    55-69 ohms
    0.9 V
    11-17%
    14.3 L (3.80 gal)

    Low Fuel Indicator Off
    70-80 ohms
    1.1 V
    14-26%
    19.3 L (5.1 gal)

    34.0 Gallon Tank (Long Bed Pickup)

    E
    40-6 ohms
    1.0 V
    4-14%
    4.5-15.7 L (1.2-4.1 gal)

    1/4
    80-11 ohms
    1.5 V
    30-36%
    43.8 L (11.6 gal)

    1/2
    117-15 ohms
    1.8 V
    50-58%
    70.4 L (18.6 gal)

    3/4
    155-195 ohms
    2.1 V
    70-80%
    97.2 L (25.7 gal)

    F
    196-250 ohms
    2.5 V
    88-99%
    123.6-126.9 L (32.6-33.5 gal)

    Low Fuel Indicator On
    61-72 ohms
    1.1 V
    11-14%
    22.7 L (6 gal)

    Low Fuel Indicator Off
    76-83 ohms
    1.2 V
    13-25%
    25.7 L (6.8 gal)

    39.0 Gallon Tank (Suburban 2500 Series)

    Important: The resistance values only reflect the specified fuel level when the signal circuits for both the primary and secondary fuel level senders are tied together.
    The fuel remaining values are approximate.


    E
    12-29 ohms
    1 V
    2-14%
    18.9 L (5 gal)

    1/4
    30-40 ohms
    1.5 V
    31-34%
    45.4 L (12 gal)

    1/2
    43-64 ohms
    1.8 V
    50-58%
    73.8 L (19.5 gal)

    3/4
    65-79 ohms
    2.0 V
    70-76%
    98.4 L (26 gal)

    F
    95-125 ohms
    2.4 V
    87-100%
    138.1-147.6 L (36.5-39 gal)

    Low Fuel Indicator On
    25-35 ohms
    1.0 V
    11-13%
    28.3 L (7.5 gal)

    Low Fuel Indicator Off
    36-41 ohms
    1.1 V
    14-16%
    30.2 L (8 gal)


    straight from gmsi. hope it helps.
    --------------------------------------------------------------------------------
    Document ID# 675267
    2002 Chevrolet Chevy C Silverado - 2WD


    In 2004 GM switched from the OLD EMPTY-40ohm FULL-250ohm to the Opposite. EMPTY-250ohm FULL-40ohm.

  7. #7
    Advanced Tuner TheMechanic's Avatar
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    Quote Originally Posted by Lotek View Post
    In your car, the fuel level sensor goes straight on the instrument panel. In Escalade, it goes to the engine control module and then on the instrument panel. It is easier to leave an old sensor 0-95 Ohms just a pcm will not see the amount of gasoline, and you and the dashboard will see
    He needs the PCM to see an actual fuel level so it can run the EVAP diagnostic.

    If you can't find a replacement aftermarket you could always run a resistor inline with the fuel level so it reads 1/2 tank so it can run the diagnostic and then flip to a full or empty resistance so the diagnostic will not run. It will likely fail if fuel level is to high or low.