How can i fix the exhaust gas recirculation flow on a mercedes-benz ml 320?

well i took my mercedes ml320 to go get smoged but the check engine light came on(i disconnected the battery to reset it and didn't know i had to drive for an hour so all the system to reboot or something) so we took it to get the check engine light diagnosis and it said it was the "exhaust gas recirculation flow" so any suggestion on how to fix this problem or what i can do my self......im just trying to pass smog!!!!! lol|||You can change the egr valve and tube pretty easy. That will fix the common issue with that code on those vehicles. IF you want you can remove the egr tube and try and clean it, but most likely changing it will be necessary.