Coolent light

When I had this problem it turned out to be the head gasket was leaking so check around your cylinder heads see if it's leaking.

I checked it and it is not leaking. One guy said check shorting on the connector to the sensor

Okay well that's good news it's not the head gasket, another thing with Saturn's is the temp sensor it's right underneath the throttle body it's drilled into the head it's a little brass thing with an electrical connector on it sometimes the electrical connector gets corroded internally or has a break in it and it could go bad I would say check that out unscrew it or whatever look at it if it's the old style it needs replaced to a solid brass 1

This is something different then thermostat correct?

Yeah has nothing to do with the thermostat but you should replace the thermostat and the coolant "get flushed" if it's been over 30,000 miles, no it's a sensor for either one of two things or both of these things depending on the model or year of the car its either going to be sending temperature information to the onboard computer or it's just going to be sending temperature information to your gauge on the dash I think on some models it shares both capabilities.