DTC P0442: Evaporative Emission System Small Leak Detected: Description

This DTC tests Evaporative Emission (EVAP) system for a small leak. Powertrain Control Module monitors Fuel Tank Pressure (FTP) sensor signal to determine vacuum decay rate. At an appropriate time, PCM turns EVAP purge solenoid and vent solenoid on. This allows engine to draw a vacuum on EVAP system. At a calibrated time, or vacuum level, PCM turns EVAP purge solenoid off, sealing system. PCM then monitors FTP sensor input to determine EVAP system vacuum decay. If PCM detects a leak larger than a calibrated amount, this DTC sets.