Exhaust gas values warning lamp

[cmyX6go]

Driving home tonight, a warning lamp comes on. I have no clue what the hell the icon represents. There are no chimes, no warning triangle in the cluster and no messages in the nav screen. I go into idrive, but don't see the icon. All systems normal. I go through each and every one just in case and all is clear. I get home - only a 12 mile trip so I'm hoping I won't explode - and open the owners manual to warning lamps. I don't see it... So I take a picture to post here.

I come upstairs and go to the online manual to take another look. I do not want to see a or be embarrassed if it's something simple. As I'm flipping through looking for the correct page number I come across it, totally by accident.

Exhaust gas values warning lamp....Now how difficult would it be to actually show the damn icon under warning lamps section of the manual ...

What does it mean? I will try tightening the gas cap as suggested in the manual tomorrow. It says something about misfiring engine. I thought I noticed excessive exhaust lately but chalked it up to the cold weather. She's been running OK otherwise.

Thoughts?

Thanks guys