Take off the top and clean out the water inlet lines from the hose connection to the inlet valves and from the inlet valves to the tub. And as long as you are in the clean out mode, clean out the pump also.

The code is telling you what you already know (funny about that), that not enough water is entering the machine. If everything checks out it may be that the valve is only partially opening. Try different temp and see if the problem is the same for all, if it is the problem is likely in the line somewhere.