Can you give me the actual "p-code" that was retrieved?
Ok- this is a "known problem" and Toyota has issued a Technical Service Bulletin that states the repair is going to need a "revised" Canister Vacuum Switching Valve.
September 29, 2003
Title:M.I.L. "ON" DTC P0440, P0441 OR P0446
Models:'00 - '03 Avalon, Camry & Solara,'01 - '03 Sienna
Under certain driving conditions, some 2000-2003 model year Avalon, Camry (NAP only) and Solara vehicles, and some 2001-2003 model year Sienna vehicles may exhibit a M.I.L. "ON" with DTC(s) P0440, P0441 and/or P0446 stored due to an inoperative Canister Closed Valve Vacuum Switching Valve (CCV VSV). The CCV assembly process has been changed to correct this condition.
It's perfectly safe to drive the vehicle, with the exception that while the VSC/Trac lights are on you will NOT have traction control. There is a "self preservation" mechanism that when the Check Engine light is on, the Trac is shut off, just in case the reason the Check Engine is on can affect/harm the trac system. Other than that, an EVAP problem will not effect engine performance in any way.
As for the cost- Toyota is not providing a price for the updated version of the CCV VSV. Probably because it's a revise, and they haven't updated the parts info to reflect the new part number. However, they state the labor to make this repair only calls for ,6hrs - so figure you'll be cahrged for a full hour of labor, which labor rates vary from shop to shop.
No bother at all...
Toyota OEM Part#: 90910-12209 - "Canister Closed Valve Vacuum Switching Valve"