DTC P0440: EVAP System - Large Leak: Description
WARNING: This page is about a different car, the 2001 GMC Savana, 2001 Chevrolet RV Cutaway, 2001 Chevrolet Cutaway, and 2001 Chevrolet Chevy Express. However, it is still accessible from the selected car via links, so may be relevant.
EVAP LARGE LEAK TEST is based on applying vacuum to Evaporative emission (EVAP) system and monitoring rate of vacuum decay. Powertrain Control Module (PCM) uses input from 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 system. At a calibrated time or vacuum level, PCM turns purge valve off (closed), and tests system vacuum. If system is unable to achieve calibrated vacuum level, PCM will set DTC P0440.