DTC P0440: Evaporative Emission System: Description

Evaporative Emission (EVAP) system large leak test applies vacuum to EVAP system and monitors the rate of vacuum decay. Powertrain Control Module (PCM) monitors Fuel Tank Pressure (FTP) sensor to determine rate of vacuum decay. At an appropriate time, PCM turns EVAP canister purge valve on (open) and EVAP canister vent valve on (closed). This allows engine to draw a vacuum on the system. At a calibrated time or vacuum level, PCM turns purge valve off (closed), and tests the system vacuum.