id get a junk yard used coolant sensor and change it. its the sensor under the t stat in the lim.
new ones are know to be bad new in the box. so either used, or find a delco.
that temp sensor sends two signals, one to the dash gauge, the other to the pcm, the pcm tells the fans to come, and that part works you say cause the fans come on. and it dont seem like its really over heating. so the dash side of the sensor is broken likely.
get a scanner on it, t app is cheap, it will tell your what the pcm says the temp is.
