Abstract: A central plug connection, especially for the connection of diagnostic apparatus in vehicles, in which a frame box consisting of electrically insulating material and equipped with at least one continuous ground rail connected with the vehicle ground is secured in the vehicle; each electrical connecting line coming from individual vehicle aggregates, is provided with a separate plug socket element that is sealingly and disengageably connected by itself at the frame box while the ground and shielding connection of the socket element is electrically connected with the ground rail; a common multi-plug is thereby adapted to be inserted into the sockets of all plug socket elements.