P1400 Nissan -

Question

how do you test the egr vacuum solenoid?

Answer 1

The EGR valve is most likely clogged with carbon built, I would try to clean the EGR and it piping first 

you can test the solenoid have you clean the EGR 

you will have to apply 12volt to the solenoid and see if the passage opens, you can blow through the port with a clean straw secured to the port, if you dont have a hand vacuum pump