2011 GMC Yukon SLT Flex Fuel 5.3 hard starts when cold

[Self]

BINGO!​

Get that reset right away, unless you're running E85! When you reset it, I believe that it also resets the LTFTs.

Not sure what part of the country you're in (?), but see the thread below for Tech 2 scanner owners; if there's one nearby, maybe get some help there.

Tech 2 Owners Map

There are quite a few members that have a Tech 2 and there are always people who wish they had one to use so I thought I would post this thread to try and help each other out. If you own a Tech 2 and would be willing to help out another forum member that might be local to you then post up your...

www.tahoeyukonforum.com

Are these in line composition sensors that accurate with percentages? I didn't even think of the percentage when I first saw it. I'll see about getting it all reset though. I live in Northwest Iowa and will take a look at that list.

If your scanner can't reset trims, I think unplugging the battery a few minutes should do it?

I'm gonna check and see. Worst that'll happen is it won't work and I'll have to use a scanner. Appreciate all the help guys!

 

[Fless]

Are these in line composition sensors that accurate with percentages? I didn't even think of the percentage when I first saw it. I'll see about getting it all reset though. I live in Northwest Iowa and will take a look at that list.

I'm gonna check and see. Worst that'll happen is it won't work and I'll have to use a scanner. Appreciate all the help guys!

Unless a physical sensor has been installed, there won't be one. In the GMT900s it's a calculation and is based somewhat on the O2 sensor readings. After you get it reset, think about replacing those O2 sensors. Mileage?

I think the battery disconnect resets only the STFTs.

Definitely let us know how it goes!

 

[Self]

Unless a physical sensor has been installed, there won't be one. In the GMT900s it's a calculation and is based somewhat on the O2 sensor readings. After you get it reset, think about replacing those O2 sensors. Mileage?

I think the battery disconnect resets only the STFTs.

Definitely let us know how it goes!

I did a bit of reading on fuel trims and it says short term is lost every time the vehicle is turned off. Long term is stored by the pcm/ecu and holds its value. It says disconnecting battery for 15 min or more should let the pcm reset and begin the long term fuel trim "relearn" over the next 50-150 miles. That's just a generic statement I found on Google so may or may not apply to the Yukon. Battery is disconnected now, so we're gonna find out. Lol. Mileage is like 184k. Doubt the previous owner replaced them so might just grab a set and do it.

 

[Self]

Left the battery unplugged overnight which did reset the long term fuel trims. They are now reading 0 until they "relearn". Alcohol fuel percentage still says 65%. Short term fuel trims are reading anywhere from -18 to -24 at the moment while cold. Have to go into work for a few hours so not able to let it get to operating temp or go out and drive it, but the hard start issue still remains. Will drive it a bit later and see what happens. Hoping with everything reset maybe I'll get lucky and it will throw a code for what's actually going wrong with it.

 

[Fless]

The alcohol composition probably will not reset without forcing it with a scan tool. I'm not sure if there was a TSB that came after the PIP document below, but after you have the alcohol % reset, you may need to have someone re-program the ECM in order to prevent future frustration. O2 sensor performance is critical, too, so if there is any question about their efficiency, replace with OE. They are considered a wear item.

https://static.nhtsa.gov/odi/tsbs/2014/SB-10069954-0335.pdf