fuel gage stuck past full

[kaspr]

2002 Silverado 1500 5.3L

The fuel gage is stuck way past full - about the 5 'o clock position - whether key on or key off. I removed the PCM wiring harnesses and tested resistance on the two wires going to the fuel level sending unit. Resistance was proper for the level of fuel in the tank, so that means the wiring and sender are ok. So that tells me it's either the PCM or the gage or wiring between the two. Is that correct?

Also, this malfunction began at a time that the battery ran way down overnight, even though no lights were left on. In the morning, when the door was opened, the dash was dinging, but nothing had been left on. The battery was disconnected and then reconnected, and battery recharged, and then tested for a parasitic drain on the battery and there was no drain - about 15 milliamps, which is very good. However, the fuel gage issue was not corrected by disconnecting the battery.

Any thoughts on what is causing the fuel gage issue and what caused that battery drain? FYI: no aftermarket electronic equipment installed.