gbynum

2011 2.2 FlexFuel engine ... they are all automatic in 2011, aren't they? Mine is.

I've read https://www.google.com/url?q=https:/...vkNxm9tdEIEE2A

which sheds SOME light ... but no resolution other than the suggestion that GM feels "We got you, SUCKER".

I began indicating self-resetting P0172 codes after my dealer did the ignition switch recall work ... but that cannot POSSIBLY be related, right?

I took it to my non GM service guy who found a somewhat dirty air filter which he changed. He found that the computer is reporting a very high ethanol %, mid-50's. He thinks the TopTier gasoline I buy isn't and asked me to run the tank a little lower (had about half) then put in some ethanol-free. Use 2 tanks and bring it back. I will, but am not driving much right now, so it may be a month or so.

Ran it down to less than 1/4 tank, filled with ethanol free, drove about 50 miles, hooked my Torque scanner up ... still over 50%. The filter must have helped, because I haven't seen a fault again. I hooked Torque back up, and am still showing between 50 and 60%. If it was 50%, it should have fallen to lower than 20% ...

Oh, my gas is from Costco and my wife's Fusion gets it when we are home. It hasn't complained. I chatted with the attendant at Costco; he doubts it (as do I) and said they check ethanol daily with an electronic device, that it is usually between 9.5% and 9.9%. They're honest to a fault in my experience.

OH ... when I got Torque last year, I checked it; the reported ethanol was about 7% ...

OK, there is something wrong ... but what ... does anyone know what the inputs are to calculate ethanol %? What would be a good path to take?

Thanks, George

donbrew

The alcohol content in gas is hardly ever what the pump says it is. Why are you agonizing over it? The ethanol gets dumped into the truck at the tank farm controlled by the truck driver, I don't want to cast aspersions on the intelligence of truck drivers but I work around a lot of them.

P0172 has nothing to do with ethanol content. (that is a period).
More likely a EVAP fault. Maybe a cracked flex pipe. Maybe somebody forgot to plug the MAF sensor back in after an air filter change.

I suggest that you stop resetting the code and do some diagnostics to find the problem. If you need to pass an emissions test just clearing it won't help.

Try this link OBD-II Trouble Code: P0172 System Too Rich (Bank 1).
And/or just google "p0172" like I did.

gbynum

Whoa, I must have said something that I don't think I said ... let me hit your points and clarify. Most important ... THANKS for your help!

My mechanic, after going over everything else, pulled that out as a POSSIBLE cause after ruling everything else out he could. His, and my research, suggest that P0172 might be caused by the overly rich condition caused by the engine properly responding to FALSE HIGH ethanol %.His thoughts too, and those wern't APPARENTLY it. And the air filter wasn't changed until after the problem arose. He thought that it MIGHT be restricting air flow and be contributing to the problem.WHOA HERE ... I never reset any code. I said SELF RESETTING ... here a while, gone a while. I VIEWED it 5 or 6 times and finally took it into the shop with no symptoms except the light and slightly lower fuel economy. The economy issue may be unrelated. His thought, after looking at multiple links similar to yours, was that the code MIGHT HAVE been related to the engine computer enriching the mixture based on the perceived alcohol content. I don't believe after three tanks full I could really have over 50% ethanol using a top-tier gasoline. He asked me to try several tanks of ethanol free and see if it came down to near zero.I, and his OnDemand5 both agree with what those links show. He went deeper ... the engine was/is running rich. He talked about the long term and short term "fuel trims" being off; economy is off a little; even with 2 more tankfuls, from darn near empty, it is still reporting over 30%. The computer runs richer, on purpose, with more ethanol. SO, what I'm trying to figure out is why the computer thinks the ethanol is high. That's just a POSSIBLE reason, and all he could find to suggest.

Back to the question; from data from which sensors is ethanol % calculated?

843de

This thread should answer your questions gby, or at least give an explanation on how HHR's detect the percentage of Ethanol in the fuel system.

Just click the link below....

https://www.chevyhhr.net/forums/gene...ex-fuel-18111/

Lucky

There is no one sensor that reads ethanol %. It uses a mutable sensors to calculate ethanol %.

You could have an o2 or a maf sensor that is not reading correctly which would give false ethanol calculations.

If you get your rich code corrected I'll bet your ethanol numbers will come back in line.

Reading high ethanol % should not trip a rich code because the computer would think it's doing the right thing by increasing the fuel mixture.

The computer shouldn't increase the mixture and set a code saying it wrong. Codes are normally set when the computer see something wrong but is unable to correct it.

donbrew

There is a module in the fuel pump assembly that measures the specific gravity of the fuel, the computer then infers alcohol content.

I have come to a complete stop now. I won't bother you any more.

hhr06NJ

how do you get ethanol free gas? i thought the STATE EPA mandates the ethanol?

on another note: a friend of mine recently told me Hi Test gas is ethanol free?

843de

Premium fuel can be either an Ethanol Blend, or what has become known as Pure Gas.

Check out the link below to see if there are any gas stations in your area selling non-blended gasoline.

Ethanol-free gas stations in the U.S. and Canada

firemangeorge

Speaking of "Pure Gas". I went by my local gas station yesterday to get some of the ethanol free gas for my lawn equipment.
Regular 87 octane, 10 % ethanol was $2.88 a gallon.
Ethanol free "Pure Gas" 89 octane was at $3.52 a gallon............Ouch!

gbynum

Thanks! That suggests the primary input is from the O2 sensor; I may have it replaced on a gamble. Noting ChevyMgr's post ... she (he?) seems gone. Did I see somewhere that GM pulled that support source?

Thanks again!