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  1. Self

    2011 GMC Yukon SLT Flex Fuel 5.3 hard starts when cold

    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...
  2. Self

    2011 GMC Yukon SLT Flex Fuel 5.3 hard starts when cold

    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...
  3. Self

    2011 GMC Yukon SLT Flex Fuel 5.3 hard starts when cold

    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...
  4. Self

    2011 GMC Yukon SLT Flex Fuel 5.3 hard starts when cold

    Key on engine off it holds pressure around 56psi. Starting and turning off it will climb up to 81psi after a few minutes and stop.
  5. Self

    2011 GMC Yukon SLT Flex Fuel 5.3 hard starts when cold

    Scanner shows 65.1% for alcohol fuel percentage.
  6. Self

    2011 GMC Yukon SLT Flex Fuel 5.3 hard starts when cold

    I'm going to have to get a new scanner that does a little more as this one just does basic code reading, abs, srs, etc. Been meaning to get a new one just haven't. Lol. It started doing it a little while ago (Octoberish) and initially thought it was my starter as it would crank a bit longer than...
  7. Self

    2011 GMC Yukon SLT Flex Fuel 5.3 hard starts when cold

    If crank sensor was dying, wouldn't that want to throw the cel on and give a code? If it would toss a code at me I'd have better luck but this thing has me guessing all over the place.
  8. Self

    2011 GMC Yukon SLT Flex Fuel 5.3 hard starts when cold

  9. Self

    2011 GMC Yukon SLT Flex Fuel 5.3 hard starts when cold

    Cold start fuel readings Short term bank 1 is -3.9 to -2.3 back and forth Long term bank 1 is -17.2 to -16.9 back and forth Short term bank 2 is -7.8 to -3.9 to -2.3 to -1.6 back and forth Long term bank 2 is -15.6 to -21.9 back and forth Close to operating temp fuel readings Short term...
  10. Self

    2011 GMC Yukon SLT Flex Fuel 5.3 hard starts when cold

    Not sure on ethanol content off the top of my head, but it's generally unleaded 87 and have been using the same gas since I purchased this in early 2021. Engine coolant temp seems to be working and reporting properly. Maf is reading 0.01 lb/s and when unplugging the engine still continues to...
  11. Self

    2011 GMC Yukon SLT Flex Fuel 5.3 hard starts when cold

    Having an issue with my 2011 Yukon SLT Flex Fuel with the 5.3. First start of the day it runs and tries to die with rough idle and will occasionally start but continue trying to start while engine is running. If it dies and I try to start it again, it will continually turn over for a good 15...

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