Low Coolant light remains on despite thyat the coolant is full on 1998 Buick Skylark

Low coolant light remains on. Sensor replaced there are no leaks. waterpump and all seals and gaskets replaced. No leaks. Pressure Tests done. Car also driven 250 miles No Problems. Is there a Diagnostic test for the circuitry and if so can you provide info re: codes? Wiring diagrams for this problem. Thank you.

Asked by for the 1998 Buick Skylark
bleed the system out air and find and clean the sensor