So, being as you are so new here. You likely have a six gallon hot water tank. That really is quite a lot of hot water. Assuming you have the tank full, and can then check what happens.
Do a measurement of a gallon in your kitchen sink, then see what the sink will hold. Assuming it might hold three gallons.... run pure hot water into the sink. As the hot water is expelled out of the top of the hot water tank, cold water enters into the bottom and mixes somewhat.
Do you get three gallons of hot hot water out of the tank? You should. If not, what happens. I am wondering whether you have a valve in the wrong position or a check valve stuck somehow.
It doesn't really explain the fault code, but it might be a place to start.