The Evaporative Emission Control System (EVAP) vent valve is used for sealing the vent. Thus, the evaporative emission control system (EVAP) pressurizes and ensures that there cannot be leaks. This valve has a 12-volt battery voltage supply with the key on.
The ground is provided by the Engine Control Module (ECM) controller and when grounded it is activated, i.e. closed. In case the Engine Control Module (ECM) detects a short to ground or a short to battery voltage in the control circuit, the DTC code P0446 OBD2 is displayed. This code also means that the ECM has detected that the EVAP system has failed to maintain a vacuum for a certain period.