I was driving my car today and the check engine light came on so I decided to stop at advance autoparts and get there little code reader and it said. System running lean (bank 2) this means an o2 sensor right and which side is bank 2 But later I was driving it and the light shut out but if I can figure out what that means I'm going to replace it anyway

 

My CEL came on 2 days ago. It made me have a dream yesterday that my car overheated and melted the hood lol. It's probably a 'dummy light' meaning it went off randomly just so I spend money having it checked out. Too bad I know everything is fine.