System Description

The control module tests the evaporative emission (EVAP) system for a large leak. The control module monitors the fuel tank pressure (FTP) sensor signal to determine the EVAP system vacuum level. When the conditions for running are met, the control module commands the EVAP canister purge solenoid valve OPEN and the EVAP canister vent solenoid valve CLOSED. This allows engine vacuum to enter the EVAP system. At a calibrated time or vacuum level, the control module commands the EVAP canister purge solenoid valve closed, sealing the system and monitors the FTP sensor input in order to determine the EVAP system vacuum level. If the system is unable to achieve the calibrated vacuum level or if the vacuum level decreases too rapidly, this DTC sets.

The following table illustrates the relationship between the ON and OFF states and the Venting or Not Venting states of the EVAP canister purge and vent solenoid valves.