Hello!!!

Ok ... here's the situation. My car has had the CEL on for quite a while. The code that comes up is 332-EGR not opening. My mechanic is the one who pulled this code and has been trying to figure out what is causing this code to come up. We have already changed the EGR solenoid, EGR valve, and the DPFE. He has also cleaned the exhaust tube to the the EGR. What else is there that can be done? And, what exactly is going on with the car to cause the CEL to come on? Perhaps I should change the O2 sensor? It seems like everyone else has this problem and the solution seems to be to change the O2 sensor. Please help me!!! My car has been to two different mechanics with no luck. If anyone can suggest anything then maybe I can go back to my mechanic with these suggestions. But, somebody please help me!!!