what is esim module
â¢ Ambient temperature must be between 4Â°C and 39Â°C (39Â°F and 98Â°F). The EVAP System Integrity Module serves as a vent and provides vacuum and pressure relief for the fuel tank and EVAP system. ESIMs are composed of a housing, small weight check valve, large weight check valve, diaphragm, switch and cover. The weights provide pressure relief by acting as one-way valve seals.