Plug connector system (100; 200; 300), comprising a pin housing (120; 220; 320) including a pin assembly (122; 222) with one or more contact pins (122A,..., 122N; 222A,..., 222N), and a socket housing (140; 240; 340) including a locking element (145; 245) and a contact assembly (142, 242) complementarily configured with respect to the pin assembly (122; 222), wherein the locking element (145; 245) is able to be coupled to the pin housing (120; 220; 320) for locking the pin housing (120; 220; 320) and the socket housing (140; 240; 340), and the locking element (145; 245) is further configured such that a part thereof penetrates through the pin housing (120; 220; 320) when the pin housing (120; 220; 320) is pushed or slid on the socket housing (140; 240; 340), and such that the locking element (145; 245), when in a locking position, is engaged with and, thus, coupled to a corresponding portion of the pin housing (120; 220; 320), the plug connector system (100; 200; 300) being characterized in that it further comprises an assurance (160; 260; 360) transversely movable on the pin housing (120; 220; 320) with respect to a plug direction between a locking position and an unlocking position, wherein the socket housing (140; 240; 340) and the assurance (160; 260; 360) comprise snap elements (146; 346, 166; 366) that are complementary to each other and that are configured to be latched in the locking position, and wherein the assurance (160; 260; 360) is further configured to be in contact, in the locking position, with the one or more contact pins (122A,..., 122N; 222A,..., 222N) for providing a secondary assurance of the pin assembly (122; 222), and wherein the assurance (160; 260; 360) is symmetric to a center plane that includes an axis parallel to the plug direction. a pin housing (120; 220; 320) including a pin assembly (122; 222) with one or more contact pins (122A,..., 122N; 222A,..., 222N), and a socket housing (140; 240; 340) including a locking element (145; 245) and a contact assembly (142, 242) complementarily configured with respect to the pin assembly (122; 222), wherein the locking element (145; 245) is able to be coupled to the pin housing (120; 220; 320) for locking the pin housing (120; 220; 320) and the socket housing (140; 240; 340), and the locking element (145; 245) is further configured such that a part thereof penetrates through the pin housing (120; 220; 320) when the pin housing (120; 220; 320) is pushed or slid on the socket housing (140; 240; 340), and such that the locking element (145; 245), when in a locking position, is engaged with and, thus, coupled to a corresponding portion of the pin housing (120; 220; 320), the plug connector system (100; 200; 300) being characterized in that it further comprises an assurance (160; 260; 360) transversely movable on the pin housing (120; 220; 320) with respect to a plug direction between a locking position and an unlocking position, wherein the socket housing (140; 240; 340) and the assurance (160; 260; 360) comprise snap elements (146; 346, 166; 366) that are complementary to each other and that are configured to be latched in the locking position, and wherein the assurance (160; 260; 360) is further configured to be in contact, in the locking position, with the one or more contact pins (122A,..., 122N; 222A,..., 222N) for providing a secondary assurance of the pin assembly (122; 222), and wherein the assurance (160; 260; 360) is symmetric to a center plane that includes an axis parallel to the plug direction.