Toyota Repair: ENGINE LIGHTS ON, charcoal canister, nearby dealer

Question
I have an engine lights on. I own Toyota Echo. I went to the nearby dealer to diagnose the problem. They told me that it is something to do with evaporative emission incorrect purge flow. They told me that I need to replace the charcoal canister. Do you agree with them? Please advice.

Thank you.

Answer
Not without being able to test the system myself and to then draw my own conclusion, it could be the canister and then again it could just be a loose gas cap,a vacuum switching valve or a leak or disconnected evap system hose, it may help if you could tell me what the trouble code was.