2006 Audi A6 engine light

MIL light came on steady this afternoon. I tightened the gas cap, still on. I don't feel feel any odd torque conversion, seems to shift smoothly accelerate normally etc. ( keeping in mind i'm not totally sure what that would sound/feel like. I just read that it was a kinda common prob for A6 models). Car idles fine and I don't notice anything different. I had just driven for probably 2hrs or so on 95, shut it off and then got back in and started it maybe 15min ltr. Could you please let me know any thoughts or ideas you have. Thanks

Sent from my BlackBerry 10 smartphone.