hey i need some help. so my car doesnt ever over heat or even get super hot but the add coolant thing is always on and buzzing. i looked under the car and it seems like theres a radiator sensor plug thing that isnt pluged in BUT i dont see anywhere to plug it please help thanks

 

The coolant level sensor is at the top of the radiator in the center. Make sure that it is plugged in.

Also verify that your coolant level is full and there is coolant in the reservoir bottle.
If all of the above is good make sure the wiring to the sensor is not grounding out anywhere.