1990 K5 Brake Light Problems

I have a 1990 5.7 K5 my problem seems simple but it''s driving me nuts I have checked all the wiring I can (Though it''s mostly covered in mud) and my park lights hazzard and turn signals work my brake lights don''t and it happened in a matter of seconds any clues as to the cause of the problem?

have you checked for voltage going into and coming out of the brake switch?

check your wires for corrossion I just replaced all my wiring for the same thing . The wires was corroded from the mud and water.