Fuel alcohol percentage relearn without going to dealer???

[Doubeleive]

Im in NC near Greensboro. I went by several shops today and asked about their scan tools. 4 had the kind of upper end scan tools that would work but either tried to tell me to get a new gas cap or to clean my MAF sensor or something like that instead of even trying to hook it up and giving it a shot. The others either didnt have the right scan tool or had no clue what I was talking about. One guy even said that since it was a former police vehicle (its a PPV model) that they probably put the wrong computer back in it when they sold it, because they take out the high performance computer when they sell them you know. I had a friend of mine who knows one of the guys at the Chevy dealer call him to see what he said and he told me to add at least 7 gallons of regular gas and then drive it about 10 miles so it might reset itself. Now its reading 60% alcohol in the tank. LOL what a day

that's funny-find another shop, they do not change the computer, they gut the pd crap out and sell it. period

 

[rockola1971]

that's funny-find another shop, they do not change the computer, they gut the pd crap out and sell it. period

That is absolutely true, they do nothing but gut the police dept gear that been added to the vehicle. Nothing is removed that the factory installed for the PPV edition vehicles.

I am curious if the alcohol content sensor in the tank has gone crazy or did you get some fuel that had incorrect amounts of ethanol?

 

[HiHoeSilver]

That is absolutely true, they do nothing but gut the police dept gear that been added to the vehicle. Nothing is removed that the factory installed for the PPV edition vehicles.

I am curious if the alcohol content sensor in the tank has gone crazy or did you get some fuel that had incorrect amounts of ethanol?

I don't believe theres any sensor in the tank. Up until 2005, it's a physical sensor on the fuel line under the drivers door on FFV vehicles. On 06+ it's called the VFFS (virtual flex fuel sensor) and it's all software.

 

[rockola1971]

I don't believe theres any sensor in the tank. Up until 2005, it's a physical sensor on the fuel line under the drivers door on FFV vehicles. On 06+ it's called the VFFS (virtual flex fuel sensor) and it's all software.

Makes it even easier to get to! But how on earth does software detect ethanol content? By the amount of spark knock and ignition retard rate that is very different from 87 octane?

 

[HiHoeSilver]

Makes it even easier to get to! But how on earth does software detect ethanol content? By the amount of spark knock and ignition retard rate that is very different from 87 octane?

Good question. It's an algorithm of some sort. I found an article once before, but I dont remember the specifics. I do, however, remember that theres a tsb/recall for the programming..

 

[rockola1971]

Very interesting. Anyone on here know a GM engineer so we can get the "truth" then we can take him out back and beat him for some of the stupid stuff they came up with that makes our maintenance 10x harder than it should be!

 

[gsd1019]

the victim is an 06 Tahoe with 5.3 flex fuel engine. Has only been run on either non-ethanol or the regular 10% ethanol gas. Im getting P0172 and P0175 codes, preventing me from getting it to pass inspection. My scan tool shows the fuel reading 46% alcohol content, which is obviously off for some reason. My research shows the high alcohol reading making it throw the rich codes. Apparently the alcohol percentage that the truck is reading can be reset to 0 or whatever with the right scan tool like the dealer has. Im trying to find out if there is a way to get it to readjust itself without having to take it in to the dealer or switching back and forth between E85 and regular gas to try to do it that way. Thanks

Just take it down to a gas station and fill it up.
Alcohol content recalibrates after a refueling event

 

[slowride]

thats what the guy at the Chevy dealer suggested. It recalibrated alright, went from reading 52% alcohol to 60% after filling up. I just turned in the tag today. Glad I have something else to drive until I can get a better scan tool or something to fix it

 

[slowride]

just to follow up, found a shop that was able to do a reset on the alcohol percentage. Fuel trims went back to low positive numbers and the cel codes went away so finally got it to pass inspection. what a pain