Systems and methods for detecting a missing coalescing element in a CV system are described. In some arrangements, the described systems and methods prevent the assembly and/or re-assembly of the CV system without an appropriate coalescing element positioned within the CV system housing (e.g., during a coalescing element service operation). In some arrangements, the coalescing element depresses a spring-loaded component of a shaft that provides flow of bypass gases to the CV system. If the spring-loaded component is not depressed, significant restriction is introduced to the CV system, and an on-board-diagnostic system may detect high-crankcase pressure through existing crankcase pressure sensors and de-rate the internal combustion engine. In other arrangements, a spring-loaded mechanism within the shaft prevents a housing cover (e.g., a lid to the housing of the CV system) from being repositioned when a coalescing element is not installed within the housing.