2015 Duramax Fuel excessive fuel consumption

[JohnDar]

With the sudden level drop in very few miles, I'm still thinking the fuel sender or maybe the gage. Watching the DIC for the fuel used, is that showing a fast drop or is it just the gage on the IP?

The fuel sender float is essentially a thin wire with a float on the end. If it gets bend or stuck, the gage will read wrong. When I replaced the OEM fuel tank with a larger 56-gallon mid-line tank, they had to adjust it a couple of times to get it to work correctly again. It still reads full until I've used several gallons and then it drops. It doesn't get accurate until about 3/4 tank. That's why I always reset the DIC reading when I fill up.

 

[DirtyMax88]

Good morning everyone. Just an update. Stop on the way home and put fuel in the truck. It took less then 2 gallons. I guess when i flipped my aux switch to transfer fuel (thinking I was actually filling the truck up), it only added a little fuel and then transferred the excess back into the aux tank. Seems like all of you that said it's in the sending unit somewhere, were correct. I am going to drop it off at the dealership today and get them to take care of it. Weird to me that something like this would happen to a truck that's only a few years old. I appreciate all the comments and insight. Thank you!