I had the same problem with my 90 buick century, Replacing the temperature sensor did the trick, it is located above and behind the water pump.
Check at the rear side of the radiator towards the top
The 2001 Buick Century came equipped with the 3100 V6 (engine code 'J'). The cooling system capacity is 11.6 quarts.
Where is the MAF in 91 Buick century
The sensor is on the back side of engine at the lip of the oil pan put installed in the engine block.
wher is the engine temperature coolant sensor BUICK 2001
under the coil pack on the 2.5 back side of the motor Dave
behind the power steering pump on the passenger side of the engine
The coolant temp sensor on a 97 Buick Century is on the side of the radiator. It is just below the radiator cap.
what is a etc sensor for a buick rendevous
The O2 sensor is right behind the engine on top of the muffler tube leaving the rear manifold on the engine. If you look down from the rear top - you can see it.
1997 buick life