Automotive plug connectors must fulfill high requirements regarding thermal and mechanical robustness as well as reliability. Ever increasing demands in function (e.g. high-voltage applications) as well as in weight and space savings create new challenges automotive suppliers must face. Functional separation and protection against aggressive or corrosive media are key requirements of most automotive connectors. Moisture and oil can interfere with the transmission of electrical signals and harm connected components by migrating through the cable strands. Thus, leakage must be minimized to avoid product failures. Overmolding is frequently used for the cost-effective mass production of connectors. Here (reinforced) thermoplastics are utilized to overmold metal conductors. Those two compound partners have different material properties that can be liable for leaks at the interfaces. Causes are either stress induced gap or crack formations. One aim of this thesis was to identify those injection molding process parameters that affect the tightness of the produced parts most. For that purpose, connectors were injection molded according to defined designs of experiments (DoEs) and tested using a bubble leakage test. They were analyzed by performing analyses of variance (ANOVAs) using the statistic software Minitab 18 by Minitab Inc. Another target was to find indicators in injection molding simulation that give guidance towards tighter connectors in advance. For that purpose, selected process setting combinations were simulated using the injection molding simulation software Moldex3D R 16 (M3D) by CoreTech System Co. Ltd. Attempts were made to gain additional information about the stress distributions by transferring data from M3D to the structural simulation software ANSYS 19.2 Static Structural (ANSYS) by ANSYS Inc. Some injection molding simulations were additionally carried out for comparison purposes using the software Autodesk Moldflow Insight 2019 (AMI) by Autodesk Inc. The findings can be summarized as follows: The ANOVAs of the DoEs identified processing factors that influenced the tightness of the produced connectors. Some quality indicators however raised concerns about the suitability of the used testing method and procedure. A relation between the found factors and a common injection molding related phenomenon could be found and further be confirmed using the simulation results. While some results matched between the different simulation software, other rather differed.