Coolant warning light has always been on since I.

Coolant warning light has always been on since I purchased this car used a couple years ago and Saturn service reps/techs couldn't figure it out or fix it at the time, after determining that it was not a coolant level, overheating, or related issue, so I have just ignored the warning light and beeping trouble indicator (tried) all this time, (and still also often check coolant regularly, just in case.) Anyway, doing a recent bit of Saturn Ion research for a another issue, I see that this coolant sensor going out is a fairly common occurence, but my manual doesn't have enough info for this type of repair or even for checking/troubleshooting. Therefore, can someone in the know, give me more details on checking and/or replacing coolant light sensor, etc? Please and thank you for any responses.