DTC P0442: EVAP System - Leak Detected: Description

WARNING: This page is about a different car, the 2002 Oldsmobile Aurora. However, it is still accessible from the selected car via links, so may be relevant.

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 and EVAP canister 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 the system, and monitors FTP sensor input to determine EVAP system vacuum decay. If PCM detects a leak larger than calibrated amount, DTC P0442 will set.

The 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 LOGIC table under DTC P0440: EVAP SYSTEM.