2011 Silverado, 5.3L. Started truck up yesterday, fuel gauge said less than 1/4 tank, 70 mile range. After two minutes or so it crept up to 1/2 tank, over 120 mile range. In traffic yesterday fuel gauge
went to empty, then back up to 1/2 full. Dash said fuel level low. Did it again, check engine light came on. Stopped, restarted truck and it worked fine rest of the day. Something is going on. Short of pulling tank and replacing sending unit, is there a sensor in the system? Something to check more easily accessible?

 

Afraid it is the sending unit, or that's what I think.

 

Back in the day, GM pickups gas gauges tended to stay on the high-side until about half a tank, then they would drop like a rock. It was when the gas tank was behind the seat.
You just got used to it as nothing is perfect, and once the gauge dropped they became pretty accurate. Yeah, 90 percent of the time it's the sender gone bad, not the dash gauge.

No one who drives a semi trusts the fuel gauge. Yes they are better now, but we would look down into the tanks, or carry a piece of wood to check the level of fuel as the gauges were so inaccurate.

The only time I had warranty work done was on my old 1970''s AMC Jeep CJ-5. The gas gauge put me on the side of the road, out of gas, but the gauge said 1/4 full. Fixed it on warranty, and it was very accurate after that.