How to reset the coolant sensor - 1999 Buick Century

There isn't a reset for it. If the coolant is full, replace the sensor.

There is no way to reset the light , you probably need a new coolant level sensor !
Coolant Level Sensor Description
The coolant level sensor monitors the coolant level in the cooling system and indicates if the coolant is low. This sensor is located at the base of the radiator surge tank and is not serviceable.
CHECK COOLANT LEVEL (2)
The IPC receives a discrete input from the engine coolant level switch. The engine coolant level switch is normally closed. When the engine coolant is low, the engine coolant level switch opens. When the IPC receives an open signal from the engine coolant level switch, the IPC displays the message on the DIC.
you have to replace this ,Radiator Surge Tank !

Try resetting the computer.If that does'nt work replace the sensor.

First if you did not reset the computer after you replaced the throttle position sensor then do so and if that fixed the problem.If it did not help then replace the coolant temperture sensor and the coolant level sensor then reset the computer.If you replace any sensor you have to reset the computer or the computer will not reconize it as being new and won't reset the perimeters for that sensor.

give the senson on the side of the coolant bottle few taps with a stick or whatever the sensor stickes in cavaliers

The only way to "Reset" your coolant light is to fill your coolant to the proper level. If the coolant is at the proper level and the light is still on, then you have a malfunctioning coolant level sensor.

coolant level sensor will be in the coolant expansion tank.

reset the computer, if no change, replace the coolant sensor, but after reset it should work

is possible your sensor inside your reservoir you need to check

This trouble is common in this models, I have one '93 ZJ and my signal Sensor Coolant Level also is ON for long time; first, try to clean the plug and reset the ECU. If the signal show again, maybe you need replace this sensor.

For more details about location and diagnotics, check this documents:
ZJ-Secc-8D-Ignition-Systems
- Page 5 Location (Coolant Temperature Sensor)
- Page 11 Diagnostics/Service Procedures
- Page 24 Removal Components

ZJ-Secc-7-Cooling-System
- Page 23 Coolant Reserve Tank (Coolant Sensor Level)

I hope help you with this (remember rated this help) Good luck.