The low coolant sensor is located about half way down on the passenger side of the radiator.First try tapping on it with the head of a screw driver a few times and see if that helps.If that didnt work remove the sensor and clean it out,it can get plugged up with that great dex-cool GM use's.If the first 2 fail then it's time to replace the sensor.
~Larry~
You can see the inside of the sensor and how it may become plugged
