DTC P0442: EVAP System - Small Leak: Description

The Evaporative (EVAP) emission small leak test applies vacuum to the EVAP system and monitors vacuum decay. The Powertrain Control Module (PCM) monitors the Fuel Tank Pressure (FTP) sensor signal to determine the vacuum decay rate. At an appropriate time, the PCM turns the EVAP canister purge valve ON (open) and the EVAP vent valve ON (closed). This allows the engine to draw a vacuum on the EVAP system. At a calibrated time, or vacuum level, the PCM turns the purge valve OFF (closed), sealing the system, and monitors the FTP sensor input in order to determine EVAP system vacuum decay. If the system detects a leak larger than a calibrated amount, DTC P0442 will set. The EVAP valve command table illustrates 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 COMMAND  table under DTC P0440: EVAP SYSTEM - LARGE LEAK.