They are pretty much little electric motors, I guess some could be solenoids but there is a lot that could go wrong with an egr valve inside. But it could also be the wiring going to the egr or the pcm itself. You need to check power and grounds to the egr valve first. If you don't get power with the key on, then you need to see if your getting power from the pcm. If your getting power at the pcm, then you have a cut wire somewhere. This test is going to require a wiring diagram. But most likely its a bad egr valve, just check the wiring for any obvious signs of damage.