DTC P0442: EVAP Control System - Small Leak Detected: Description
WARNING: This page is about a different car, the 2002 Pontiac Sunfire, 2002 Pontiac Grand Am, 2002 Oldsmobile Alero, and 2002 Chevrolet Cavalier. However, it is still accessible from the selected car via links, so may be relevant.
EVAP small leak test applies vacuum to Evaporative Emission (EVAP) system and monitors vacuum decay. PCM monitors Fuel Tank Pressure (FTP) sensor signal to determine vacuum decay rate. At an appropriate time, PCM turns EVAP canister purge valve on (open) and EVAP vent valve on (closed). This allows engine to draw a vacuum on EVAP system. At a calibrated time, or vacuum level, PCM turns purge valve off (closed), sealing system, and monitors FTP sensor input in order to determine EVAP system vacuum decay. If system detects a leak larger than a calibrated amount DTC P0442 will set.