Circuit Description

The DTC P0446 Evaporative Emissions (EVAP) Vent System Performance diagnostic monitors the performance of the EVAP system vent routine. Ignition voltage is supplied directly to the EVAP canister vent valve solenoid. The Powertrain Control Module (PCM) closes the vent valve by grounding the solenoid control circuit using an internal solid state device called a driver. When the valve is closed, the FTP sensor will indicate a drop in pressure in the EVAP system during purge activity. If Fuel Tank Pressure (FTP) sensor values do not correspond with vent valve activity, a DTC P0446 will set.