Outline Of Diagnosis
Monitor Method
This monitor intrusively performs a functional check to detect incorrect purge flow when the engine is running in very high boost conditions.
Theory of operation: At very high boost conditions, the pressure drop caused by the air filter creates a slight vacuum in the high pressure purge line. Refer to following Figure 1.
Phase 1: The monitor removes the air in EVAP system by closing the ELCM switching valve and ELCM pump is intrusively activated when the solenoid valve for high pressure purge is open and all enable conditions are satisfied. In the case of normal condition, ELCM pressure (gauge) will decrease to reach the threshold value. However, if the hose is disconnected, the ELCM pressure will remain above the threshold value.
Phase 2: Since there is a possibility that a large amount of EVAP vapor is generated during Phase 1, the monitor may determine a false fail. To prevent this condition, the EVAP system is sealed and the pressure is measured after a predetermined time (following Phase 1). If the measured pressure exceeds a second threshold value, the monitor is cancelled. If the pressure does not reach the second threshold value, the monitor determines a malfunction (disconnection).