check engine light

We have a V that has been at the dealership because they cannot figure out why the check engine light won't turn off. They've had it for several days and I assume have checked all the normal culprits and its still on. Anyone had this happen? Any advice?

 

I will get the code (something about intake manifold) but they replaced whatever the code was for and light still won't go off. Almost a week of additional diagnostics have yielded nothing.

edited to add: Thanks for the response. I hope someone here can help provide some insight!