Fuel gauge 0 and low fuel warning with DTCs

[wildrness27J5]

My 2002 2500HD Silverado, 6.6 Duramax, 270K miles, Bully dog tuner and throttle response adapter. Purchased truck a few months ago with this problem and like to try to solve it. 

When ignition switch is  first turned on all reads normal for 12 seconds, then the fuel gauge will drop to empty and low fuel information light will illuminate. truck is Showing the following DTCs: P1093, P1094, P1283, P1621. Once fuel gauge drops the radio will also turn off and reset clock to 1:00 and volume will drop to minimal. When I clear the DTCs the fuel gage reads normal and low light goes out, radio will power back up if turned on. Truck runs fine (though I do not think it is making as much power it is capable of), no lope, mild hazing under load turbo 18+ boost (24 max attainable), and I get about 19mpg on no tune setting with tuner, 14-15 mpg with 100hp tow tune set. I have uninstalled the tuner with no change in behavior. Are the DTCs linked to the fuel gauge / warning system? I'm looking for a scanner so i can pull fuel rail pressures and balance data. Suspecting the FPRV on CP3. Any hints would be welcome. Thank you.