The mechanic has explained to me that the engine is not getting hot fast enough. The thermal gun agrees with what the computer is seeing. The engine temperature needs to be 3 degrees hotter for the alarm to clear. Since the thermal gun and the computer agrees, they ruled out the sensor and replaced the thermostat. Engine light is still on. I checked the resistance of the ECT and found to be constant at 3500 ohms. That's 50 degrees F. It hasn't been 50 F here in PA for awhile. What I don't understand then, where is the compuer getting its information from?

 

Engine/year?

That statement is confusing. You seem to show sensor is not measuring accurate temp.Are you saying the sensor should haveresistance equal to above 50F? IfECTmeasured 53F then light would clear? Did you use thermometer to measure engine coolant temp?