DTCS P0442 Or P0455: EVAP System Leak - Small Leak/Gross Leak: Description

With engine running, and vehicle speed is 35 MPH or more consistently, ECM closes EVAP canister vent valve and opens EVAP canister purge valve. If EVAP control system is okay, EVAP control system pressure detected by fuel pressure sensor is lowered. When EVAP control system pressure is lowered, ECM closes EVAP canister purge valve, leaving EVAP canister vent valve closed. If EVAP system is okay, fuel tank pressure will increase to a predetermined level.