2004 Saturn Vue coolant sensor
 

Coolant temperature sensor indicator light comes on intermittently.
Can I replace the sensor or do I have replace the coolant tank?

Try removing the reservoir and cleaning it with dishwashing liquid. Then rinse it really really really really really really well. Also note that some of these sensors actually since the downward pressure of the liquid above. So it does not take much of a volume loss to trip the sensor.