I just bought code reader : Actron OBD II AutoScanner CP9175 because there is law in California that only dealers can read the codes. So i connected the thing and it said " no code" or something similar. So i get back and they said that that is ok. Any way i changed the reader for new one and still the same. Have i mind that when i disconected the baterry my check engine light turned off and fuel thing didn't show up again.
What filters should i change? They changed oil filter when i changed oil. Should i change air filter too? Fuel filter? Spark plugs?

Ohh...and thank you all for help so far. I realy apreciate it