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Thread: Tech 2 ?

  1. #1
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    Default Tech 2 ?

    Does the Tech 2 tool allow you to modify/calibrate the E-F lines of the fuel gauge?
    07 Chevrolet 2500 NBS LTZ 4x4 6.5'Box xCab

  2. #2
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    No, it doesn't. It is a GM fuel gage. You'll have to resort to paper/pencil, or commit the formula to memory. Or, do like the rest of us, and guess.

    However, if your needle has just moved out of the blue, to a new range, you can use a Tech II to compare the BCM/PCM reported fuel level % to the gage reading. If the gage matches the %, then the sender is going away. If they are different, then the gage is going away. In any case, the gage is a dumb-slave, and only indicates (supposedly) the % of the fuel level data in an analog display.
    1985 Blazer 6.2
    2001 GMC 2500HD D/A
    dmaxmaverick@thedieselpage.com

  3. #3
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    Default

    Gauge has a 25% error / reading low by 25%
    07 Chevrolet 2500 NBS LTZ 4x4 6.5'Box xCab

  4. #4
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    Default

    My 07 classic 2500 was dead on, my 07 NBS 2500 has a 25% low error.
    07 Chevrolet 2500 NBS LTZ 4x4 6.5'Box xCab

  5. #5
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    Sounds like a tank sender error. Perhaps the float is bent, defective, or something. If it's consistent, but just regularly off by a specific level, I'd suspect the sender. It could be the gage, with the needle off position. Bad parts happen, even when new, on a new vehicle. A check with a Tech II would identify the source.
    1985 Blazer 6.2
    2001 GMC 2500HD D/A
    dmaxmaverick@thedieselpage.com

  6. #6
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    I think this is the age old "why do I only put 2x gallons in my 26 gallon tank when I refill at the low fuel light" thread.

    I believe from a possible email conversation the tank takes 19 gallons from the low fuel light. I don't recall what I add to my 07, but I seldom run to the low fuel light. Not sure if and why the new body style would be any different.

    I could recalibrate the gauge to go deeper, but a larger Titan tank (and recalibration) is the ultimate answer. That way you can get the range and still leave several gallons in the tank.
    Kennedy Diesel-owner
    More than just a salesman-I use and test the products that I sell on a daily basis!
    Superflow Lie Detector in house
    2002 Chev K2500HD D/A CC Long LT 11.77@ 124mph at 7700# fuel only-e.t. needs help
    2005 Chev K3500SRW D/A CC Long LT(SOLD)
    2007 Chev K2500 Classic EC Short LT (Sold)
    2012 GMC K3500SRW D/A CC Long LTZ Happy Birthday to me! Built 1 working day after my birthday and delivered 7 days later.
    2016 GMC K3500SRW D/A CC short LTZ

    Custom tuning in house using EFI Live tuning software!

  7. #7
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    Default What causes....

    Are there separate sensors for the low fuel light and the gauge indication?
    07 Chevrolet 2500 NBS LTZ 4x4 6.5'Box xCab

  8. #8
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    Default Checking Accuracy

    Checking accuaracy of gauge so I have a reference point. It just seems to go down so fast....
    Off by 1/4 tank
    07 Chevrolet 2500 NBS LTZ 4x4 6.5'Box xCab

  9. #9
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    There is only the one sensor: the fuel level sender in the tank. The "gallons used" in the DIC does not use the sender value, but the "miles remaining" uses the value to detect a fuel fill and fuel remaining. Check this value against what it should be after a full fill. If it seems about right with your average MPG (for previous 50 miles) and actual fuel remaining in the tank, the gage is probably the problem. If it calculates well short, then the gage is likely suspect, but that may not be accurate if it isn't obvious, such as missing 1/4 tank of fuel while parked or stable driving on a level surface.

    If that doesn't help......
    If it is indicating 1/4 tank less than (actual) full to empty, but is relatively linear, the gage or sender is suspect. You'll need to check the datastream fuel level % value with a Tech II or similar scanner. If it matches the gage indication, the sender is failed/failing. If it tracks the fuel level in the tank, but is about 1/4 different than the gage, then the gage is failed.
    1985 Blazer 6.2
    2001 GMC 2500HD D/A
    dmaxmaverick@thedieselpage.com

  10. #10
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    The sensor voltage to gallons is mapped out in the ECM which then drives the dash cluster.

    Accuracy is only generalized, but good enough in most cases. Now if a guy were to run until empty, then add fuel until the charted voltages are achieved it could be mapped out I guess.

    I don't see that we have the attachment upload capabilities that many other forums do or I could upload a screen shot.
    Kennedy Diesel-owner
    More than just a salesman-I use and test the products that I sell on a daily basis!
    Superflow Lie Detector in house
    2002 Chev K2500HD D/A CC Long LT 11.77@ 124mph at 7700# fuel only-e.t. needs help
    2005 Chev K3500SRW D/A CC Long LT(SOLD)
    2007 Chev K2500 Classic EC Short LT (Sold)
    2012 GMC K3500SRW D/A CC Long LTZ Happy Birthday to me! Built 1 working day after my birthday and delivered 7 days later.
    2016 GMC K3500SRW D/A CC short LTZ

    Custom tuning in house using EFI Live tuning software!

  11. #11
    Join Date
    Mar 2010
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    Default Update

    The other week I was checking fuel gauge accuracy. Tank = 26 gallons
    Used 19 gallons low fuel light turned on gauge pegged at empty. I continued for another 120ish miles until DIC showed I used 24.5 gallons. Then I was getting nervous and filled up.
    07 Chevrolet 2500 NBS LTZ 4x4 6.5'Box xCab

  12. #12
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    Mar 2010
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    Default Verification

    Dealer told me 4-5 hours labor to diagnoste. At 115/hr ouch.

    This is such a Great Group
    07 Chevrolet 2500 NBS LTZ 4x4 6.5'Box xCab

  13. #13
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    Mar 2010
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    Default Dash

    Can the fuel gauge be repaied or are we talking a whole new cluster ?
    07 Chevrolet 2500 NBS LTZ 4x4 6.5'Box xCab

  14. #14
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    OK.

    The fuel level and low fuel indicators both operate off of the tank sender. The DIC fuel usage does not, and is only useful for diagnosis if the average fuel mileage and miles remaining are calculated in. If the low fuel message and fuel gage both indicate the same (low fuel message and empty on the gage), but you still have ~7 gallons in the tank, I would suspect the tank sender. While a IPC stepper motor failure isn't unusual, it doesn't look like it at this time. It should be confirmed with a scanner before throwing time and money at it.

    4-5 hours to diagnosis a fuel gage issue is insane. It takes me 15 minutes or less, or maybe up to an hour if it's a real bear (wire harness damage, for example). 4-5 hours is enough time to diagnose the cause, then replace the tank sender and IPC, including a couple union breaks and a leisure lunch. Insane.
    1985 Blazer 6.2
    2001 GMC 2500HD D/A
    dmaxmaverick@thedieselpage.com

  15. #15
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    Mar 2010
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    Default Info

    Alittle ove 1/4 tank left, indicates 13.1 gallon used
    At 1/8 left 16.7 gallons used
    At E 19.0 gallons used/ 46 mile range/ 18.7 mpg which does not cculate into 7 gallons. Is there anyway to diagnose without a Tech2 tool?
    07 Chevrolet 2500 NBS LTZ 4x4 6.5'Box xCab

  16. #16
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    Quote Originally Posted by silvdur View Post
    Alittle ove 1/4 tank left, indicates 13.1 gallon used
    At 1/8 left 16.7 gallons used
    At E 19.0 gallons used/ 46 mile range/ 18.7 mpg which does not cculate into 7 gallons. Is there anyway to diagnose without a Tech2 tool?
    Yes. With that info, it looks like a tank sender. I still recommend verifying with a scanner. There are MUCH less expensive options (~$20), than a Tech II. Email me and I'll let you in on the secret.
    1985 Blazer 6.2
    2001 GMC 2500HD D/A
    dmaxmaverick@thedieselpage.com

  17. #17
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    Default

    Quote Originally Posted by silvdur View Post
    Alittle ove 1/4 tank left, indicates 13.1 gallon used
    At 1/8 left 16.7 gallons used
    At E 19.0 gallons used/ 46 mile range/ 18.7 mpg which does not cculate into 7 gallons. Is there anyway to diagnose without a Tech2 tool?
    Are there any aftermarket devices, ECM programmers etc on the truck?

    H&S?
    Kennedy Diesel-owner
    More than just a salesman-I use and test the products that I sell on a daily basis!
    Superflow Lie Detector in house
    2002 Chev K2500HD D/A CC Long LT 11.77@ 124mph at 7700# fuel only-e.t. needs help
    2005 Chev K3500SRW D/A CC Long LT(SOLD)
    2007 Chev K2500 Classic EC Short LT (Sold)
    2012 GMC K3500SRW D/A CC Long LTZ Happy Birthday to me! Built 1 working day after my birthday and delivered 7 days later.
    2016 GMC K3500SRW D/A CC short LTZ

    Custom tuning in house using EFI Live tuning software!

  18. #18
    Join Date
    Mar 2010
    Posts
    55

    Default Follow Up

    Truck is all factory, no programmers.
    I purchased truck used 07 w/35,000 miles.
    Added a Prodigy beake controller for towing.
    Have no clue what H&S?
    07 Chevrolet 2500 NBS LTZ 4x4 6.5'Box xCab

  19. #19
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    Mar 2010
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    Default Purchaed this year w/35,000 miles.

    Purchased this year w/35,000 miles
    07 Chevrolet 2500 NBS LTZ 4x4 6.5'Box xCab

  20. #20
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    Mar 2000
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    The reason I ask is that most tuners affect the DIC calculations (put not the gauge itself) to the positive side, but some (H&S) seem to skew the opposite direction.
    Kennedy Diesel-owner
    More than just a salesman-I use and test the products that I sell on a daily basis!
    Superflow Lie Detector in house
    2002 Chev K2500HD D/A CC Long LT 11.77@ 124mph at 7700# fuel only-e.t. needs help
    2005 Chev K3500SRW D/A CC Long LT(SOLD)
    2007 Chev K2500 Classic EC Short LT (Sold)
    2012 GMC K3500SRW D/A CC Long LTZ Happy Birthday to me! Built 1 working day after my birthday and delivered 7 days later.
    2016 GMC K3500SRW D/A CC short LTZ

    Custom tuning in house using EFI Live tuning software!

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