Brake light stays on
 

My brake light stays on for my 1999 Plymouth Voyager van.
I can unplug the sensor cable from the connection below my brake fluid resevoir and the light goes out.
My brakes work.
Do I have a bad sensor is is somthing else wrong?
What does it usually mean when my brake light comes on with this sensor. The brake fluid resevoir is full.

low brake fluid is what the sensor is for on the master cyl

Thanks! That is what someone else told me as well.