Check engine

I have a 2001 toyota camry LE. The check engine like was on a few weeks ago. I read the error code on the computer. It seems there was something wrong with the air intake system. I changed the air filter. The check engine light went off after I filled the gas. But it went on again now. I think it may because of the fuel system. I manage to change the oil filter and clear the fuel injection. Will these be help?

Start by posting the exact code, Pxxxx. Someone may be able to help you after the real code is posted.

I forgot the code, may be P0420.

  That CEL (check engine light) is just a kid in class waving her hand trying to get you attention because she has the answer. You need to have the codes read. Some places will read them for FREE. Try Autozone or Advanced Auto Parts. Get the exact code (like P0123) not just their translation into English and post it back here. 

 It is sometimes possible to read the code after the light goes out.

homebovine–

Code P0420 indicates that the catalytic converter is not operating at its optimum, and there can be multiple explanations and fixes when that code comes up.

However, you said that it “may be P0420”. Just as you would not want a surgeon to operate on you, based on a “may be” diagnosis, it would be a good idea to confirm exactly what code(s) are present before going any further with this thread.