queencie59 , More info, such as year,engine size could of helped. Find below listings for the Buick temp. sensor locations.
2.2 (4 cyl.) The coolant temperature sensor is located on the
passenger side by the alternator, see link #1.
3.1l and 3.3l similar, temp sensor is located at the thermostat housing, link #2
Good luck.
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https://www.youtube.com/watch?v=ShLu0nAd2AY
http://www.autozone.com/repairinfo/repairguide/repairGuideContent.jsp?pageId=0996b43f80cb1d5f