Have you checked the coolant level?
Even a good sensor can't read any temp if the coolant level is low and yes that'll cook your motor and likely blow a head gasket.
2nd guess would be a stuck thermostat, but it should at least register "some", as in up higher than when it's not running, key in Run.
You should paste from the PMs, you've gotten a lot of good advice, including the fan clutch.
Coolant level, replace the thermostat, it may be a bad sender - check its connection, and also take off the radiator cap, then start it. Goose the gas while you watch the coolant level in the radiator (keep your face away). It should FLOW when the thermostat opens and you goose the gas. It'll take a while to warm up to that point. No flow could be a bad water pump.
Don't open a hot radiator cap.
^^Like he said, the coolant sensor has ONE WIRE, not two. Should be in the front, near and behind the top radiator hose. The two wire one is for the computer. Use a paper clip to ground out that one wire, while someone watches the gage. It should go to full HOT pretty quick. Un ground it or turn the key off so you don't blow a fuse.