PROBLEM! A bad connection, adj of sensor, moister and or mud. Maybe a failed part.
A code reader can tell you much more. Have it checked, you don't want to be without good brakes.
04 Horizon QD, 12 Ford Flex, Excalibar, Brakemaster, Winter Texan, RVin! since 1974
Norm, Donna & Tinker Kat 74 MGB-GT, 75 MGB, 01 Z3
Life is a Timed Event, you only get One Go Around!