Purpose of Mode Z

When performing the leakage diagnosis of EVAP system, CPC have to operate normally. Therefore, mode Z is used to diagnose the CPC open fixation.

If the CPC open fixation trouble is detected, the EVAP system leakage diagnosis is cancelled.

If the CCV closed fixation trouble occurred, negative pressure is generated from the engine to pressure control solenoid valve when pressure control solenoid valve is closed and CPC is opened. Under this condition, the valve cannot be opened for the pressure control solenoid valve structure if the negative pressure is larger than electromagnetic force when pressure control solenoid valve solenoid is set to ON in order to open the valve.

Fig 1: Purge Control Solenoid Valve Blocking Diagram - Open Trouble Diagnosis

Courtesy of SUBARU OF AMERICA, INC.

Fig 2: Sectional View Of Purge Control Solenoid Valve Components

Courtesy of SUBARU OF AMERICA, INC.