Fuel Gauge Issues?

steve76t · January 14, 2020

I have a 2017 GMC Sierra 1500 Denali that recently started having issues with the fuel gauge. Three fill ups ago I noticed that the fuel gauge didn’t quite get to the full line. A little driving & it got up to about the 7/8ths line, but didn’t get to full. Next fill up same thing. Yesterday it barely got to the same 7/8ths line & is dropping quickly. Only 30 miles into this latest tank & its already down to the 3/4 line.

Anyone else have or had this issue? What’d ya do to fix it?

Phil Murray · January 14, 2020

Float issue? Don't know how these measures but it used to mean that the float was saturated.

davester · January 14, 2020

Could be float, could be wiring, could be sensor, could even be the instrument panel..

steve76t · January 15, 2020

May have to take it to the stealership to see what they can do. On my commute this morning the gauge started out between the 3/4 and 7/8 lines. 10 miles later it was below the 3/4 line. At lunchtime I headed out to run some errands and the gauge was back over the 3/4 line. Weird stuff...

steve76t · February 18, 2020

Finally had time to get the truck to the dealership today. Was told that there appears to be very common issue with fuel sending units this winter. Service mgr told me that there's some sort of additive in the fuel this winter that's creating the problems. In Reno NV we have oxygenated fuels, primarily ethenol + some other additives, that help reduce vehicle emissions during the winter months.

This issue is so common that the dealership is having 15 to 20 vehicles per week with fuel sending units reading low. Most stop at about the 3/4 line on the fuel gauges. They're seeing vehicles from all GM lines coming in with the problem including GMC, Cadillac, Buick, etc. All being 2015 and newer vehicles.

For now the fix may be to simply clean the fuel sending unit and electrical contacts and reinstall it. If the issue takes more than a quick cleaning then they'll order a new sending unit. May even order a new one regardless. We'll see how this goes.

For the record, their story does kinda make sense. I took a road trip to Las Vegas in late January. On the return trip I topped off my gas tank in Tonopah NV, they don't have the same oxygenated fuel that is found in Reno or Las Vegas, and continued on my way home. Noticed about 100 miles from Tonopah that my gas guage was still reading about 3/4 of a tank. When i got home I filled up at my regular gas station and my guage read nearly full! WooHoo! Highest it read in more than about a month. Not quite full but very close. However, at the next fill up this past weekend it was back to just under 7/8 of a tank.