A method for manufacturing a sealed electrical wire harness includes the steps of providing an equipped connector housing with electrical terminals inserted within the equipped connector housing and with electrical wires attached and electrically connected to the electrical terminals, providing an injection molding tool suitable for injecting sealing material, placing the equipped connector housing into the injection molding tool, closing the injection molding tool, filling the equipped connector housing with sealing material, thereby distributing the sealing material inside the equipped connector housing to a wire inlet portion, a connector position assurance holder portion, and an interface portion, and removing the sealed electrical wire harness from the injection molding tool.