These are great machines, but the GE engineers had a field day in making them complicated.

The fill level is contained in the control programming. Take off and clean and re-seat the P5 connector on the control board and see if that fixes things. Not likely, but it is worth a try. Also follow the wiring from the P5 connector and check all of its connection forward and check the wiring for any problem.

There should be some tech notes inside the lower service panel. Use them to see if you can put the machine into diagnosis mode and generate error codes.

If all this does not fix things replacing the control board is the next thing you try.

Good Luck, wish we could be more specific.