Technical Description

To judge if there is a leak in the fuel system, ECM (M/T) or PCM (A/T) measure the change of pressure in the fuel tank.
The ECM (M/T) or PCM (A/T) turns on the evaporative emission ventilation solenoid valve to shoot off the evaporative emission canister outlet port.
Then the evaporative emission purge solenoid valve is driven to set the fuel system into a negative pressure.
When the fuel system develops a vacuum of 0.29 psi (2 kPa), the evaporative emission purge solenoid valve is turned "off" and the fuel system vacuum is maintained at 0.29 psi (2 kPa).
The ECM (M/T) or PCM (A/T) determines if there is a leak in the fuel system by measuring the change of vacuum inside the fuel tank. The test is stopped when fuel vapor pressure is judged as too high.