Circuit Description

PCM tests EVAP system for a large leak. PCM monitors Fuel Tank Pressure (FTP) sensor signal to determine EVAP system vacuum level. When conditions for running DTC are met, PCM commands EVAP canister purge valve open and EVAP vent valve closed. This allows engine vacuum to enter EVAP system. At a calibrated time, or vacuum level, PCM commands EVAP canister purge valve closed, sealing the system, and monitors FTP sensor input to determine EVAP system vacuum level. If system is unable to achieve the calibrated vacuum level, or the vacuum level decreases too rapidly, this DTC sets.