1999 Chevy Cavalier Sensor that turns on fan belt

you want to know what sensor helps to turn the electric radiator fan on. there are a couple. of course the radiator fan relay must be working in order for this to happen anyway, so you must verify that the fan works by hardwiring the fan to the battery, if it comes on,obviously its good. but also the engine coolant temp sensor, will tell the computer that its too hot, then in turn the computer will send a ground to the fan to make it come on

Thank you. Yes it has been hooked to the batter and tested. It does come on and therefore works. So i was told that the sensor may be bad. So this being the case, you said its called the engine coolant temp sensor?...

yes, engine coolant temperature sensor