fuel gauge

I have an '01 4door 4WD Blazer. From a full gas tank down to half, the gauge works well. From half tank and below, the gauge will drop to "dead Empty" and the low fuel light will come on. If you wait long enough, the problem corrects itself. You can get an instant correction by shutting off the engine and then re-starting. This will immediately correct the reading. Chevy has tried twice by replacing parts to no avail. HELP!!!