I'm wondering if anyone has any knowledge with the Evaporative Emissions Control(EVAP) system. My vehicle is throwing a Code P0455. I've already replaced the gas cap and the code has returned. Today, I took off the assembly that houses the EVAP canister, check valve, dust seperator and canister vent solenoid. I noticed the check valve( big white plastic valve ) appears to be stuck open. I feel this because you can blow air through both ends. You don't have to blow hard at all for air to go through it. It never really seemed to be closed. Would this throw a Code P0455? I have a 2001 Mazda Tribute.