Dumb question : one of my friends was checking out my car and he opened the oil cap on the engine while the car was running...I heard the rpm change a bit and shortly after i got a CEL...I know for a fact that if you dont tighten the gas cap, it can throw a CEL... is that something similar for this as well?

 

I had a 1999 that I left the oil cap off after I changed the oil the last time and it did trigger the CEL. Autozone reset it for me and it never came back on.

 

That happens because the engine gets air that the MAF hasn't seen and the system goes lean. Except for the crankcase vent the crankcase is essentially sealed. The SES light would have reset by itself.