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Thread: E38 fuel level sensor calibration

  1. #1
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    Default E38 fuel level sensor calibration

    One thing I didn't care about in my swap (2007 5.3 LMG in 1997 2dr 4wd Tahoe)
    is the fuel level sensor. I had to built a new connecting rod for the level sensor, 'cause the '97 Tahoe's gas tank is a lot deeper than the 2007 composite tanks.
    I also had to modify the fuel pump module to fit that deep tank.










    The manual states 40ohms resistance for a full tank and 250 ohm resistance for the empty tank. The E38 sees 5V for the empty tank and 0V for the full tank. In my 1997 Tahoe gas tank I could manage to have 250ohms empty and 50ohms full.... not exact but close to the spec.

    Then I looked up the calibration in EFIlive : There is F0504 which is the tank capacity in liter and F0505 as sensor calibration.
    I have F0504 113l. When I read those values with the scan tool:



    I recieve 0.8V for a full tank. Seems ok so far but what seems strange to me is I read 99l as Fuel tank rated capacity GM.FTRC although I programmed F0504 113l in the tune tool.



    any ideas? Did I miss something?
    best regards from Germany

    Harald
    If nobody has done it before, somebody has to do it....

    1997 Tahoe 2dr 4WD
    2002 Alfa Romeo Sportswagon 2.0 JTD
    1982 Deutz Intrac 2004A
    2003 friesian Horse " Henry"

  2. #2
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    Quote Originally Posted by harascho View Post
    One thing I didn't care about in my swap (2007 5.3 LMG in 1997 2dr 4wd Tahoe)
    is the fuel level sensor. I had to built a new connecting rod for the level sensor, 'cause the '97 Tahoe's gas tank is a lot deeper than the 2007 composite tanks.
    I also had to modify the fuel pump module to fit that deep tank.

    The manual states 40ohms resistance for a full tank and 250 ohm resistance for the empty tank. The E38 sees 5V for the empty tank and 0V for the full tank. In my 1997 Tahoe gas tank I could manage to have 250ohms empty and 50ohms full.... not exact but close to the spec.

    Then I looked up the calibration in EFIlive : There is F0504 which is the tank capacity in liter and F0505 as sensor calibration.
    I have F0504 113l. When I read those values with the scan tool:

    I recieve 0.8V for a full tank. Seems ok so far but what seems strange to me is I read 99l as Fuel tank rated capacity GM.FTRC although I programmed F0504 113l in the tune tool.

    any ideas? Did I miss something?
    best regards from Germany

    Harald
    Nice mod there Harald.

    Does the ECM OS you are using normally look for a 2 sensor setup?

  3. #3
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    Default fuel sensor setup 2007 Tahoe

    good question...
    I am using the following VIN of a 2007 Tahoe as data source.
    The ECM, TCM, BCM, Cluster and TCCM are updated via TIS to the latest tunes based on that VIN

    1GNFK13037R238413

    As far as I know a Tahoe only uses one fuel level sensor but I am not 100% sure..

    Harald
    If nobody has done it before, somebody has to do it....

    1997 Tahoe 2dr 4WD
    2002 Alfa Romeo Sportswagon 2.0 JTD
    1982 Deutz Intrac 2004A
    2003 friesian Horse " Henry"

  4. #4
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    Default another effort







    Maybe I'm wrong, isn't GM.FTRC exactly what I set with F0504 in the tune??? If yes then there is something wrong cause a F0504 of 113litres returns a GM.FTRC of 99litres regardless what I do with F0505.

    I would expect if I set F0504 to 113litres that I can see this in GM.FTRC as 113 litres and that the calibration of F0505 then should be set to 113litres at 0V fuel level sensor voltage?



    a still confused Harald
    If nobody has done it before, somebody has to do it....

    1997 Tahoe 2dr 4WD
    2002 Alfa Romeo Sportswagon 2.0 JTD
    1982 Deutz Intrac 2004A
    2003 friesian Horse " Henry"

  5. #5
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    Default some logs

    if anyone is interested here are the logs
    Attached Files Attached Files
    If nobody has done it before, somebody has to do it....

    1997 Tahoe 2dr 4WD
    2002 Alfa Romeo Sportswagon 2.0 JTD
    1982 Deutz Intrac 2004A
    2003 friesian Horse " Henry"

  6. #6
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    At a guess, 99L tank is probably the max size that is catered for by the OS/fuel segment. The number may have scope to get above 99 like your 113L, but there is more to the fuel cal than just the tables shown.

    If your gauge reflects the sender level, then the cal is probably for a single sender tank. If it was a two sender tank, then it would do wierd things with one sender. (based on first hand experience ).

  7. #7
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    Default

    ok, I did a bit of searching for you. The PID value you see is not actually derived from the sensor scaling and calibrations, instead it is just a single calibration value that is used solely to report the fuel tank size, so it's almost useless. This is why you don't see anything change.
    Need official EFILive help, please go here.
    For tuning support please post your questions on this forum (or other auto forums).
    Sorry if I don't respond to your PM, don't take it personal.


  8. #8
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    Does your OS have F0505 "Primary Fuel Tank Sender Calibration"? If it does, just use it to recalibrate your gauge to read correctly with the different tank/sending unit setup. Raising values makes the gauge read higher, lowering them lowers gauge reading.

    Oh, just re-read your posts, you do have F0505 but it doesn't seem to be changing? Do you mean the gauge itself isn't changing? It should. Try putting some drastically different numbers in F0505 and see if your gauge reads differently. I wouldn't worry about it if F0504 doesn't change.

  9. #9
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    Default sensor calibration

    'had some spare time today. I connected a poti to the fuel level sensor inputs of the E38 and did some research.

    I divided the gas gauge scale in 8 sections E to 8/8 (F).
    Then I checked which resistance I need with the calibration on top of this thread to have the gas gauge exact at the 8 levels I created. In the same time I watched the FLS and FuelRem with the scan tool.

    Here we are:




    Interesting that the min sensor Voltage is 0,84V at 50R and the max sensor Voltage is 2,53V at 250R fuel level sensor resistance.... The table in the tune file starts at 1,4 V - 5V . It looks like there is factor 2 somewhere between?

    Adjusting the F0505 to the values of my table brought no success. I ended with 6/8 gas gauge reading at 50R level resistance..?
    I reloaded the tune file above and the gaugedidn't read that bad.... I made a big circle and ended at my starting point.... or are my thoughts wrong ?

    Harald
    If nobody has done it before, somebody has to do it....

    1997 Tahoe 2dr 4WD
    2002 Alfa Romeo Sportswagon 2.0 JTD
    1982 Deutz Intrac 2004A
    2003 friesian Horse " Henry"

  10. #10
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    Quote Originally Posted by harascho View Post
    'had some spare time today. I connected a poti to the fuel level sensor inputs of the E38 and did some research.


    Interesting that the min sensor Voltage is 0,84V at 50R and the max sensor Voltage is 2,53V at 250R fuel level sensor resistance.... The table in the tune file starts at 1,4 V - 5V . It looks like there is factor 2 somewhere between?

    Adjusting the F0505 to the values of my table brought no success. I ended with 6/8 gas gauge reading at 50R level resistance..?
    I reloaded the tune file above and the gaugedidn't read that bad.... I made a big circle and ended at my starting point.... or are my thoughts wrong ?

    Harald
    Admirable achievement getting this working as well as you have.

    All late model GM fuel level setups we have seen run with a 0-2.5V range.

    Yes the port for the fuel level offers a standard 5V supply when measured with a meter, but the output impedance/resistance of the port is roughly equal to the total tank sensor resistance, so 2.5V across the tank sensor.

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