This code is constantly pinging at me. I replaced the coolant temp sensor near the water pump/snoot, then replaced the level indicator sensor in the overflow reservoir. No dice.
The 5.9 has no clutch fan, so the electric fan is activated using two sensors which are in-line with the upper radiator hose and the lower radiator hose. My fan seems to be working normal, so I assume (and hope) it's not one of these babies ($75/each from dealer).
It's keeping cool, running normal temps all the time.