low brake fluid message

on my p38 range rover i have got a bleep sound and a mesage comin up saying low brake fluid i have check the brake fluid and it is still full i have also checked the sensor which sits on top of tank next to the cap plz could someone give me some info on what it could be.

no funny comment or answers please!

try cleaning the connections. i'm sure someone will give you info on testing the sensor with a multimeter but i would test for a resistance change and continuity first!