DTC P0442: EVAP Control System Small Leak Detected: Description

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

For the relationship between the on and off states, and the open or closed states of the EVAP canister purge and vent valves, see EVAP VALVE LOGIC  table under DTC P0440: EVAP SYSTEM.