My check engine light came on yesterday, So i had the code pulled and its the EGR valve but when i was under the hood i noticed i was missing a cap on a part and was wondering if it was the problem. Figured if anyone could help it was you guys. Pic included
P.S. Not my engine just an example

 

Nevermind everyone my check engine light turned itself off. It was on for three days and on the way to school just turned off

 

I can't be sure because I don't have the same car as you, but I think that is the access/filler port for the a/c system. (or whatever the technical name for that thingey is) It is for filling the system with freon. The plastic cap is just a dust cap/cover, nothing critically important.

The code went away, that is good. That means that you completed 3 full drive cycles with the problem not appearing. That does not mean it will not reappear though, so keep an eye on it. EGR valve replacement is easy though, so don't sweat it.

 

Thanks for the reply. I wasnt worried about the EGR valve replacement its just 70 bucks i dont have to spend now