DTC P0442: Evaporative Emission Control System - Small Leak Detected: Description

The Evaporative Emission (EVAP) small leak test applies vacuum to the EVAP system and monitors vacuum decay. The PCM monitors the Fuel Tank Pressure (FTP) sensor signal to determine vacuum decay rate. At an appropriate time, the PCM turns the EVAP canister purge valve and vent valve are turned on. This allows engine to draw a vacuum on EVAP system. At a calibrated time or vacuum level, PCM turns purge valve off (closed), sealing the system, and monitors the FTP sensor input in order to determine EVAP system vacuum decay. If system detects a leak larger than a calibrated amount DTC will set.