FFDP

iTrader: (2)

You will want to verify if your have a real sensor or a virtual sensor through. Even though it's a E85 or flex fuel truck does not always mean it has a real sensor that is accurate.

The older GMT-900's that are flex fuel trucks all run what they call virtual sensors that use the fuel trims to determine alcohol content. It's not a very accurate way to read it and it is very slow to react to the changes unlike a real sensor that could figure it out in just a few minutes.

I always hear of people having issues when they try to blend fuels or run one tank of E85 then switch back to 93 octane, the virtual sensors will take forever to adjust the calibration back.

Gorske

13.96 pass was a K&N drop in filter, muffler swap, and e85 tune.

1994Vmax

iTrader: (4)

2014+ trucks run a real alcohol sensor in the fuel line. Even the 2500HD's do as they have been that virtual trash in the past like the 1/2 ton GMT900's.

FFDP

iTrader: (2)

The 2500's must be after 2015 as the 2015 file I have still says virtual sensor from the factory.

1994Vmax

iTrader: (4)

Its funny because HP or whatever is wrong there... says that same virtual or whatever BS on my 17 HD too. But yep.. crawl under the truck and there sure is an alcohol sensor in there just like the 1500 series trucks. Although all the gas HD trucks have a sensor you can still get a half ton without e85 capability and I could see those being virtual and it's probably a labelling thing on the interfaces end at that point.

FFDP

iTrader: (2)

Silly hpt.

1994Vmax

iTrader: (4)

Plus the HD has a stupid ECM that is shared with cool cars like Cruzes... and has minimal support. The E78 is kind of worthless.

FFDP

iTrader: (2)

Yeah it baffles me why they used that controller. The E38 was just fine for everything else up to 2013 in the half ton market and then like 2012 hits they decide to screw with things for the heavy duty line.

1994Vmax

iTrader: (4)

Yup. We shall see if I even can get e fans working properly on it or not. The Suburban HD has them but that doesn't mean much lol.

00pooterSS

iTrader: (40)

Damn that's it.. badass

Thanks for the heads up and the info

I knew something was funny with the older flex fuel gm's. I've had a couple come in the shop with rich codes and found nothing wrong, except that they were in fact running rich. I reset the fuel adaptive tables and the problem goes away. I realized since it went away after resetting the adaptive tables that it was fueling for fuel that had high alcohol content, but didn't have fuel in the tank that had high alcohol content, so they were dumping extra fuel and they had a rich mixture due to that.