Here's the long answer:
Your fuel level sending unit has a variable resistor attached to a float inside the fuel tank. As you use fuel, the float changes position (downwards) causing the variable resistor to change value. The change in resistance causes a change in the voltage sent to the fuel gage.
The P0463 error is saying that the variable resistor is showing zero resistance instead of a typical small value. This means that the variable resistor or something else inside the sender unit is causing the ECM to "see" an invalid (13.8 V?) voltage on the fuel gage circuit.
Time for a new sending unit...