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Thread: '12 5.3 ethanol calculation TSB update?

  1. #1
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    '12 5.3 ethanol calculation TSB update?

    I've got a stock '12 Silverado LC9 that was run with E85 one time and every since it's been stuck saying the alcohol percent is 66.7% even after resetting LTFT's and 4 full tanks of E10. Start rough when cold, commands 10.82:1 AFR and LTFT's quickly go to -30% and I get rich codes. I know there is a TSB saying this happens and the dealer has an updated calibration to reset it, looking through the calibration on the VCM editor I can't see what could be changed that would fix this/be associated with the TSB. I tried setting the max ethanol percentage to 15% and flashing that but the scanner still says 66.7% when idling.
    Any ideas what the updated calibration looks like? Thanks!
    2001 2500 silverado 4x4 ex. cab sb lq4 western 7.5' cable plow

  2. #2
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    Has it been tuned at all? MAF or any adjustments made. The algorithm will always be off due to this. I have installed that calibration at the dealer many times, I thought it was older trucks though like 07-10 I can check in a bit. Best to disable factory virtual flex fuel. I advise all customers to never use any e85 unless an actual sensor has been installed and is reading correctly.

    Other issues for the factory algorithm to be off are intake/vacuum leaks, rear exhaust bolts broken? (Additional unmetered air hitting o2 sensors, skewed o2 sensors, MAF sensor skewed, aftermarket air filter, aftermarket intake.) Pretty much any thing related to air sensors or components that are not perfect will cause this issue. I had a brand new valvoline air filter cause this on a truck a couple months ago. It just didn't flow the same as a factory filter and threw off the calculations.

  3. #3
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    Just like HardH20 said, disable the virtual flex fuel mode. It will cause problems otherwise.
    If you want to run E85, just add a sensor and enable it in your tune.

  4. #4
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    Quote Originally Posted by HardH20 View Post
    Has it been tuned at all? MAF or any adjustments made. The algorithm will always be off due to this. I have installed that calibration at the dealer many times, I thought it was older trucks though like 07-10 I can check in a bit. Best to disable factory virtual flex fuel. I advise all customers to never use any e85 unless an actual sensor has been installed and is reading correctly.

    Other issues for the factory algorithm to be off are intake/vacuum leaks, rear exhaust bolts broken? (Additional unmetered air hitting o2 sensors, skewed o2 sensors, MAF sensor skewed, aftermarket air filter, aftermarket intake.) Pretty much any thing related to air sensors or components that are not perfect will cause this issue. I had a brand new valvoline air filter cause this on a truck a couple months ago. It just didn't flow the same as a factory filter and threw off the calculations.
    Bone stock, the only tuning I had done to it previously was to set the misfire threshold higher because it would stop going into v4 mode on the highway at 70mph if it "rumbled" in V4 mode going up a hill. It would then stay in v8 mode till the next time the truck was started. Would set a MIL occasionally. That was a couple years ago. I have a couple drums of neat ethanol I'm trying to burn up to get rid of and was splash blending 5 gallons of it when I'd fill up the tank with 87e10. After doing that for a couple tanks it began starting rough when cold and setting MIL's for being too rich so I stopped blending. I let the tank get down to about .5 gallon before refilling all the way for 3 tanks or so and it never helped the rough idle. I finally fixed my MPVI (bad usb cable) and was able to see that the ethanol estimate was pegged at 66.7% still and LTFT's were pegged. It's like it isn't doing the relearn, maybe I should have tried refilling the tank with KOEO, never did. I dug through the repository and compared earlier trucks with my calibration and the "flex fuel" tab has exactly the same values so I'm curious if the difference was in the calibration or deeper in the ecu somewhere. HPTuners doesn't seem to have access to the "3 gallons of fill up" threshold I read about that's supposed to set the virtual sensor off. I did notice that on the K2xx trucks it looks like they went back to using an inline sensor like in the gmt800's. Wonder why GM was trying to cut costs in 2007 with the gmt900?

    I first tried re flashing the same calibration back to the ECU to see if it would clear the ethanol percentage, but it didn't which I thought was odd. 2 hours with the battery off didn't either.
    I don't have E85 available anywhere near me, wish I did, so this is a pretty isolated instance. I ended up disabling flex fuel in the calibration and it's running fine now. LTFT's less than 10%, it looks like when you disable flex fuel mode it assumes E0 gasoline so it makes sense it's off a little bit. Do the MBT spark tables account for ethanol content? I assume not but I'm wondering if I'm missing out on a small bit of MPG with the ethanol content set to 0% instead of 10%?
    Since I couldn't regular run E85 I doubt it would ever make sense for me to put a sensor in (daily driver, not one of the fun toys).
    Next summer I'll be trying to burn the ethanol off again so I'll be revisiting this, thanks for the help!

    Edit: I did have a broken drivers rear manifold bolt around this time that was starting to make a tick when cold, but I fixed it (Dorman clamp thing, lifesaver)
    2001 2500 silverado 4x4 ex. cab sb lq4 western 7.5' cable plow

  5. #5
    Tuning Addict 5FDP's Avatar
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    Change the stoich table to 14.1 and that will reflect the E10 fuel you are running.
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

    If you don't post your tune and logs when you have questions you aren't helping yourself.

  6. #6
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    Agreed. I've been noticing that slot lately. Most people don't seem to know to set stoich to 14.109. Everyone is stuck at 14.7 still. I wonder how many people are fighting just that aspect in their tunes

  7. #7
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    I've run E10 fuels for years with stoich left at 14.68 in some of my vehicles because I just didn't care enough. The minor work the fuel trims had to do didn't bother me lol.
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

    If you don't post your tune and logs when you have questions you aren't helping yourself.

  8. #8
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    Good to know. I would have thought it has more of an impact.

  9. #9
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    Quote Originally Posted by 5FDP View Post
    I've run E10 fuels for years with stoich left at 14.68 in some of my vehicles because I just didn't care enough. The minor work the fuel trims had to do didn't bother me lol.
    What about spark advance? Are MBT and knock limited region spark tables affected by ethanol content?
    2001 2500 silverado 4x4 ex. cab sb lq4 western 7.5' cable plow

  10. #10
    Tuning Addict 5FDP's Avatar
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    Yes they are but going from E0 to E10 isn't going to make an difference.
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

    If you don't post your tune and logs when you have questions you aren't helping yourself.