how to disable flex fuel?

[slowride]

Tired of having issues with my 06 Tahoe 5.3 FFV, fuel alcohol percent staying at 60 for the past couple tanks and its running like crap. Can the Chevy dealer or someone go in and disable the flex fuel? Thanks

 

[TollKeeper]

It would be easier to just replace the inline E-Sensor (dont know the exact name of it). A tech2 might be able to recalibrate it?

 

[Fless]

It would be easier to just replace the inline E-Sensor (dont know the exact name of it). A tech2 might be able to recalibrate it?

Called a Fuel Composition Sensor. It may also help to update the PCM/ECU calibration before making any physical changes. A Tech 2 used with TIS2000 (or Tech2Win online) can check and update the calibration, as can a dealership.

EDIT: what happens if you simply disconnect the FF sensor that's on the fuel rail?

 

[slowride]

thanks for the replies. This model has the "virtual' sensor that needs to be disabled. If I knew what to unplug it would be gone. Ive had this thing reset so many times now that the guy at the shop just hands me his tech tool when I pull up. I went by the local Chevy dealer to ask about any ecm update to fix the issue and that went nowhere

 

[Scottydoggs]

a lot of the time them sensors need to be reset, as far as i know it can only be done with a tech 2. causes the fuel trims to go nuts and the engine wont run right.

as far as deleting it from the tune. pretty sure it can be turned off with a mouse click.

 

[Fless]

You can enter your VIN here and go through a few steps to see if a calibration has been released to cure this type of issue:

TIS

If you want help with it, post up (or PM) your full VIN and I'd dig through the calibrations.

EDIT: you can also ask Blackbear or DiabLew if it could be disabled in a custom tune.

 

[slowride]

Thanks for that info. Will look into if a custom tune can do it. If there is a way the dealer can do it, I would also like to know so I could try explaining it at a different dealership

 

[Fless]

Sent you a PM with details.

EDIT: Look for any calibration that would affect fuel composition.

 

[Mudsport96]

If your computer is seeing alcohol levels high, it is probably bad intake gaskets or o2 sensors. The virtual flex system sees the tank refuel then calculates the composition of oxygen in the exhaust with the o2 sensors.
There isnt anything in the flex system to fail.
There is an update as i just had it done to my 06.
But i would start with new o2 sensors and check for leaking intake gaskets first.

 

[Fless]

If your computer is seeing alcohol levels high, it is probably bad intake gaskets or o2 sensors. The virtual flex system sees the tank refuel then calculates the composition of oxygen in the exhaust with the o2 sensors.
There isnt anything in the flex system to fail.
There is an update as i just had it done to my 06.
But i would start with new o2 sensors and check for leaking intake gaskets first.

If you go that direction, just look at your fuel trims to see if they're in the ballpark.

 

[slowride]

This was from the other day. The fuel comp learn mode doesnt always activate after refueling, and I mean 10 or more gallons each time, then randomly it will activate the next time and go from 20% to 50% to 27% then stop on something like 50%-70% within like 2 minutes. I'll check other things like 02 sensors, but bottom line I want to delete/disable anything related to flex fuel operation on this thing, Im tired of it

 

[Scottydoggs]

-20 is rich af. content sensor might have gone bad too.

 

[Mudsport96]

Get some carb cleaner and spray around where the heads and intake meet, and where the clamps are on the intake tube. See if it is getting unmetered air somewhere. Also, if it is not recalculated every fill up more than 10 gallons you may need the update.

 

[Mudsport96]

 

[Fless]

View attachment 351608

While that's a good example, below is what the calibration history looks like for the OP's VIN. Slightly newer calibration for the engine. As well, there are other non-engine calibrations that can affect the fuel composition calculation.

 

[jwth]

a tuner with hptuners or efilive can disable it and remove the error messages,,,but it is not free. There is a cost for the licensing for the software and I would assume for the owner of the tuning rig.

 

[Mudsport96]

While that's a good example, below is what the calibration history looks like for the OP's VIN. Slightly newer calibration for the engine. As well, there are other non-engine calibrations that can affect the fuel composition calculation.

View attachment 351609

Odd that they are both 06s and there are 2 different os updates...

 

[slowride]

Thanks a lot for the info. So is that calibration # something I could take to a dealer and the should know what Im talking about upgrading? I checked the Tech II owner list post but didnt see anyone near me in NC with one. Will also look into the cost of one of the custom tunes and whats involved with loading that on my ride. I got some gas today and now Im showing 63% alcohol lol

 

[Fless]

Thanks a lot for the info. So is that calibration # something I could take to a dealer and the should know what Im talking about upgrading?

Yes. Updating the calibrations shouldn't take much time. I'd think less than an hour's worth of shop time. They do it all the time. But discuss your concerns before you have them update.

 

[Mudsport96]

Ran me 62 bucks in the middle of Illinois. 20 minutes shop time