Stick it 2 ya

Recently while driving, The Yellow "Service Engine Soon" light came on. I've heard different things about it such as the fuel cap, catalitic converter etc.

The only thing out of the ordinary about my car is the K&N pop in filter I have inside. I tried calling the dealer but they are closed Sundays (I hate Sundays). What does this light mean? I've noticed no change in performance at all and the car seems normal. Just for the hell of it, I checked my fuel cap, looked under the hood for loose wires/hoses, and replaced my K&N filter with a regular Fram air filter. This light just came on the day after I had my car at the dealership to install the data dots. Could the dealer have made the light come on to warrant another visit from me? or is something really wrong?

Please......... no flames. I can't search.

SE01

Probably the famous 0420 code. It basically is saying that there is something wrong with a catalytic converter but there really isn't, it's just the compter being stupid. Take it to the dealer and have it reflashed and you should be good. Just to make sure, bring it to AutoZone and have the code read.