Coolant temperature sensor/1999 buck century - 1997 Buick Century

This is for the V6 engine, hope it is what you wanted.

Your cooling sensor is in the white plastic coolant tank that is on your firwall under the hood. If you fill it with coolant and the light continues to stay on. try and slap it a few times and see if that resets it. it could be gunked up. if that doesnt work fill the tank with radiator flush and let it sit for a little while and then flush the tank and refill with coolant.

A variety of sensors provide information to the ECM/PCM regarding engine operating characteristics. These sensors and their functions are described below. Be sure to take note that not every sensor described is used with every engine application. Coolant Temperature (ECT) The Engine Coolant Temperature Sensor (ECT) is a thermister (a resistor which changes value based on temperature) mounted on the engine coolant stream. As the temperature of the engine coolant changes, the resistance of the coolant sensor changes. Low coolant temperature produces a high resistance (100,000 ohms at 40°C/40°F), while high temperature causes low resistance (70 ohms at 130°C/266°F). The ECM/PCM supplies a 5 volt signal to the coolant sensor and measures the voltage that returns. By measuring the voltage change, the ECM/PCM determines the engine coolant temperature. The voltage will be high when the engine is cold and low when the engine is hot. This information is used to control fuel management, IAC, spark timing, EGR, canister purge and other engine operating conditions. A failure in the coolant sensor circuit should either set a Code 14 or 15. These codes indicate a failure in the coolant temperature sensor circuit.
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It looks like the above, under hood, passenger side, upper engine area, mounted in front side of water outlet (according to Autozone.com).

Top left side of the engine, below the throttle body

does your car temp gauge show bad reading? sounds like your temp sensor is going bad

BELOW THE THERMOSTAT HOUSING ON DRIVERS SIDE OF ENGINE

your buick century has a low coolant level sensor located in the passenger side of the radiator , sometiomes the sensor get covered with coolant sludge and will show that the cooling system is not filled , sometime the radiator is just still low on coolant . check the radiator when the engine is cold ( IF HOT WAIT !!! 30 mins ) and make sure the level is above the sensor.

is there coolant in the system ? if there is go to the coolant bottle there is a sensor in the bottom of that bottle if there is any thing beside coolant in that bottle it will cause the sensor to act erraticly. if there is no coolant our low coolant then the sensor is working you need to look for a leak