Virtual E85 fuel relearn?

[Devin]

Hello, starting off with nowhere near a tuner and very new to the mvpi2. just got done doing a DOD delete and went to fill up the truck (08 silverado 5.3) and got codes P0172 and P0175 system to rich on both banks. looked into it and found alcohol percent to be at 30%. seen that this is fairly common issue with the virtual e85 sensors. E85 has not been ran in the truck since i have got it so there is no mix of fuel. my question is where would i got to "relearn" or "calibrate" this sensor? truck is all stock. any help is appreciated, thanks!

[5FDP]

If you own HP Tuners and the MPVI just turn it off in the tune.

Otherwise you need a nicer scan tool that can reset the fuel composition. The one in the VCM scanner never worked for me.

[blindsquirrel]

E85 Flex Fuel Description

E85 compatible vehicles no longer use an alcohol sensor to determine and adjust for the alcohol content of the fuel in the tank. Instead, the vehicle calculates the alcohol content of the fuel through measured adjustments.

The ethanol calculation occurs with the engine running after a refueling event has been detected via a measured change in the fuel level sender output. The virtual flex fuel sensor (V-FFS) algorithm temporarily closes the canister purge valve for a few seconds and monitors information from the closed loop fuel trim system to calculate the ethanol content. This logic executes several times until the ethanol calculation is deemed to be stable. This may take several minutes under low fuel flow conditions such as idle, or a shorter time during higher fuel flow, off-idle conditions.

Air-fuel ratios and the corresponding ethanol percentage are updated following each purge-off sequence. The fuel alcohol content percentage value can be read on a scan tool.

When an E85 compatible vehicle is built, an ECM or PCM replaced, or if the learned alcohol content has been reset with a scan tool the fuel system will need to contain ASTM gasoline with 10 percent or less ethanol content.

A minimum of 11 liters (3 gallons) must be put in the tank in order for the vehicle to recognize a re-fueling event. It is not necessary to turn the ignition OFF in order to have the re-fueling event recognized, however local safety regulations should be followed.

After the re-fueling event, the system registers the amount of fuel that was added, relative to the amount that was in the tank. Reading fuel trim and O2 sensor activity, the system determines if the fuel added was either ASTM Gasoline or ASTM E85. Based on that determination, the system adjusts to the expected alcohol mix in the fuel tank, and then the fuel trim and O2 sensor activity fine tunes the adjustments. The system must remain in closed loop in order for this adjustment to occur. Numerous short trips after switching from gasoline to E85, or E85 to gasoline, can result in driveability symptoms due to the inability of the system to adjust for fuel composition by not attaining closed loop operation.

Switching Between Gasoline and E85

No special precautions need to be taken when switching back and forth between gasoline and E85 other than re-fueling events must be 11 liters (3 gallons) or greater, and the vehicle must remain in closed loop long enough, usually by the time the engine has maintained full operating temperature, to calculate the composition of the new blend in the tank.

see also: 'too clever by half'

[Alvin]

Hello, starting off with nowhere near a tuner and very new to the mvpi2. just got done doing a DOD delete and went to fill up the truck (08 silverado 5.3) and got codes P0172 and P0175 system to rich on both banks. looked into it and found alcohol percent to be at 30%. seen that this is fairly common issue with the virtual e85 sensors. E85 has not been ran in the truck since i have got it so there is no mix of fuel. my question is where would i got to "relearn" or "calibrate" this sensor? truck is all stock. any help is appreciated, thanks!

I vote to disable Virtual Flex fuel. It doesn't work well at all.. Even in completely stock applications.

The setting for it is [ECM] 201

[Devin]

[QUOTE=Alvin;708221]I vote to disable Virtual Flex fuel. It doesn't work well at all.. Even in completely stock applications.

The setting for it is [ECM]

I did see where I could disable it. I was not sure if disabling it would allow it to reconfigure the current content of the fuel or if it would still be stuck at 30. I dont run E85 so it wouldn't hurt a bit to turn it off for the future. Thanks for the quick replies!

[Alvin]

It usually resets it.

[2xLS1]

I did see where I could disable it. I was not sure if disabling it would allow it to reconfigure the current content of the fuel or if it would still be stuck at 30. I dont run E85 so it wouldn't hurt a bit to turn it off for the future. Thanks for the quick replies!

Disabling it forces it to use the stoich value in 0% column in the stoich table.

[Roblamont80]

I know I am a year late on this but it is one of the reasons I bought a HP tuner. I was going to jump in and disable E85. My question is, since fuel has 10% ethanol in it, will that cause the truck to run lean? Or will this be adjusted by the ECU to off set for the less efficient fuel composition? Probably much better than running lean. I also reset mine weekly with my bi-directional scan tool. I also do large fill ups and take longer drives after fill ups of 7-10 gallons and still have huge discrepancies in fuel composition.

[blindsquirrel]

https://www.google.com/search?q=e10+...lter=0&start=0

screenshot.26-12-2023 16.58.26.png

[1scls1z]

set virtual sensor to disabled, then go into the stoich table shown in picture above, set it to 14.67 for E0 across the entire table or 14.1 for E10. If you want to run the E15 88 octane set to 13.8. Or you could probably set it to 13.9 and go back and fourth between E10-15. I doubt it will make a big difference either way.