21 Mustang GT Check Engine Light Under Hard Acceleration/Cornering and Low Fuel.

Discussion in '2015+ S550 Mustang 5.0L Tech' started by David Darius, Sep 14, 2021.

  1. David Darius

    David Darius Junior Member

    Hey guys, had a small and hopefully resolved issue come up on my new 2021 Mustang GT Convertible with under 1000 miles. Recently, had four people in the car and gave it a little gas, 4-5,000 RPM max into a corner and then for a few seconds, maybe 30 or less, my check engine light started flashing and then turned off. I only had about 20 miles of range/fuel at that moment.

    The FordPass app messaged me minutes later stating that a warning light was triggered by a possible engine misfire or poor fuel condition. I did not feel or hear any possible engine misfire and would not have known anything happened if not for the flashing check engine light.

    My thinking is that having been low on fuel and having accelerated hard into a corner, that perhaps the fuel pump or system felt it had less fuel available given the G forces moving fuel around and triggered the light which then turned off when I let off the gas. I did refuel the car after that and with some similar driving, did not have the light come back on the next few days. Well, it only flashes when I turn on the electrical/accessory power and not the gas engine and then turns off immediately when the gas engine is on.

    Just today, I also received my monthly FordPass vehicle diagnostics report which showed no problems. Local Ford dealer said to have it checked out at next service if the light is gone now.

    Has anyone here had a similar issue or have any thoughts about this? Let me know, thanks!

    P.S. Car has been driven moderately hard as new, has not been redlined or abused much, lol.

  2. LarryJM

    LarryJM forum member

    I would say you had less the 1 gallon in the tank.
    David Darius likes this.
  3. Dino Dino Bambino

    Dino Dino Bambino I have a red car

    Your CEL came on because your fuel pump was momentarily starved of fuel as you were taking a corner. Allowing the fuel level to drop that low is completely unnecessary and risks burning out the fuel pump. My low fuel warning light comes on when the range is 50 miles to empty but I routinely add fuel as soon as the fuel gauge needle drops below 1/4. At 1/4 tank my on board computer usually shows a range of about 80 miles.
    crjackson2134 and David Darius like this.
  4. Olerodder

    Olerodder Junior Member

    I had quite a few issues with fuel lights and running out fuel more than once because of the fuel transfer module that pumps fuel from one saddle tank to the other, and also when driving with low fuel levels. Personally, I would never let the tank get less than 1/2 to 3/8 empty before gassing up. My initial issue was when the gauge would show 1/4 or less I'd be driving along and all of sudden the gauge would drop to E and the 5 mile warning would appear, which meant if I didn't find a gas station with 10 miles or so I was going to be sitting beside the road. This happened 3 times and stranded me 15 miles from civilization. Ford did come to the rescue and they put it on a flatbed and straight to the dealer. Once when it ran out of gas, I put 2 gallons in it and drove it to the gas station and it only took 9 gallons to fill it up.
    David Darius likes this.
  5. 86GT351

    86GT351 forum member

    David Darius likes this.
  6. David Darius

    David Darius Junior Member

    Yes, I will be more careful from now on.
  7. riffraff

    riffraff Junior Member

    Also, keeping a quarter of a tank in it keeps the pump cooler; it's fully submerged.
    David Darius and crjackson2134 like this.
  8. Mitchr85

    Mitchr85 Junior Member

    Tell my wife that! She never gets gas until the gas light has been on in her CRV. Drives me crazy...but that's a short drive;)
    David Darius and crjackson2134 like this.
  9. David Darius

    David Darius Junior Member

    Very true, I'll stick to the refuel when near 1/4 tank rule from now on.
  10. Iceman62

    Iceman62 Bullitt 6005

    $50K sports car + <1-gal fuel = CEL

    There's the math...;) :D
    David Darius likes this.
  11. Juice

    Juice forum member

    I have been on track till the low fuel light came on. Hard cornering, and no CEL. I feel some of this info is a myth. If 11 gallons filled the car from empty, there is something not quite right.
    I believe when my low fuel light comes on, there is about 2 gallons left, and I have gone up to 30 miles (not on track) after light came on to date.
    That has been my experience.
    I should find out just how far I can go past the low fuel, with a 5 gallon can in trunk, drive till it runs out. I have no worries doing that once. Shit, still running the original fuel pump. lol
  12. Jack F

    Jack F Junior Member


    There is no such part.
    DieHarder likes this.
  13. jewc75

    jewc75 S197 Junkie S197 Team Member

    Most of us that switch from e85 to 93 run down to 1 mile left and never have issues. The 21's may be different though. Cant even tune them yet.
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