The levels are topped off,there are no leaks, and the strength of the Dex cool has been tested strong? At only 48,400 miles is the sensor in the resevoir bad?

Any constructive response appreciated.
Thanks

if the coolent light is blinking then you may need a new ECT sensor(common, do a search here for ECT)

if the coolent light is steady then the level sensor may be bad or just stuck(it uses a float)