I have this issue going on for over 10 years. But I never got to fix it because emission issues was not a problem in the city I lived. Now I moved I had to deal with this problem. I just had my first check passed after changing something but I did not think it was really changed or if it worked it worked only 60 miles. I passed the new driving requirement for driving cycle

Any way, I tested the check engine light again at Toyota dealership and they replaced the gas cap but never worked. Every test seems now to have passed with thumbs up or infinity but am not sure of what it is. It did not make any difference with the check light engine on. Should I just ignore it or should I have to fix it. I see no problem on the car but wondered if it is possible to get rid of this problem once and for all. Different mechanics come with various test diagnosis some telling there is failure in solenoid, catalytic, evap , etc. and advised me to consult a mechanic but no mechanic said if there is anything wrong.
The codes are usually three or two consistenly

P404
p441
P406
Something with EVAP and catalytic converter.

Others told me to change the whole charcoal canister back in 2005 but never believed them.

Anyway, thanks

 

Your question seems to be a matter of opinion of whether you should fix something or not. In that regard, do what you want. I would like the stupid light out personally, I think it is annoying to have it lit up on the dash cluster.
Are the above codes what is being displayed right now?

 

What year and engine type?

How is the MPG, dropping?

 

It may not be required to have your emission system repaired in your region but, you are required to be healthy. most gasoline these days use benzene, the fumes from burned benzene can cause cancer. When your car is running, there is a vacuum behind your car that sucks air. The air that are being sucked back includes your emission from tail pipe. If you decide to fix this issue, I have found some free guides at youcanic. Hope this helps.