The Evaporative system may have problems with the vapor canister releasing charcoal pellets that plug the vent valve. Typically a Code P0441, P0442 and P0446 will be set. The key code is the P0446 which is a vent valve electrical failure. The proper repair is to replace the entire canister with all the valves as a unit. This is located on top of the fuel tank and is expensive. Our Technicians tell us that for awhile Toyota was covering these problems, but this may have changed. It would not hurt to call the dealer if this problem occurs to see if Toyota is still helping with these repairs.