Invention patent application for one Lock Controller (1) made in a cast casing fitted with a closure lid (2) designed with a bearing for the solenoid (3) guiding axle (3a) and one micro-processed control unit (4), being said Lock Controller (1) installed in the free niche (C) of the bottom half of the fifth wheel (5) where the hole (5b) is made through the wall (5c) in order to allow the passage of the extension (1d) of the Lock Controller (1) and one hole (6a) made into the Locking bar (6) face coinciding with the wall (5c) limits the course and one safety ring (8) is welded or glued at section (7a) of the long rod (7), to limit its course.