One day my truck with 31K miles was going along great....I check my gauges frequently... then the overheating waring light came on. Finding that odd, that it was 30 degrees outside, and a cold engine, was throwing that light. I stopped thinking it might be a stuck thermostat. I felt the tank, upper hose and lower hose...all normal. I started the truck up again and the light went out and the temp gauge went to straight up normal temp. Next day I was about 30 miles from home and the light came on again. I stopped, did the underhood check as above. Started it up again and the light was still on ... trying to get to my destination I put it in gear and it was running very rough then went into 'limp' mode. It stopped again and refused to restart. Called AAA. Dealership read the codes (P1285, P1289, P1299) They then did more diagnoses and replaced the CHT sensor. Got it back today and it seems ok. (part # 9L8Z6G004F)

 

All normal. Cylinder head temp is used to bias timing and fuel. If the sensor goes out of range, it's limp mode time.