You would need a digital volt meter a vacuum gage, and vacuum pump to diagnose. Disconnect the EGR vacuum hose and install a vacuum gage. Raise the the idle to see if there is vacuum to that hose. There should be no vacuum at idle. When you accelerate you should see some vacuum about 5psi or a little higher. If there is no vacuum check the vacuum source at the solenoid valve. If that is ok remove the EGR solenoid vent valve. I am posting the 2 pictures up as to the procedure to check the vent. You can blow through the valve if you have no vacuum pump. If you have a vacuum pump then just pump vacuum and install vacuum gage at the other end of where you need to check for the flow. Here are the steps.
1) Verify that air flows as shown in image.
2) If not as specified, replace the EGR solenoid valve (vent).
After use the vacuum pump or just blow through see second image for flow.
3) Apply battery positive voltage to terminal A and ground terminal B of the EGR solenoid valve (vent). Verify that air flows as shown in image.
4) If not as specified, replace the EGR solenoid valve (vent).
Also with it disconnected with the key on engine off, verify there is battery voltage at the connector. If voltage is present then turn key off and at the other terminal measure resistance from the other terminal to battery ground. You should see something under 1 ohm. If that is good then you know the circuit is good. Most likely the vent solenoid is faulty and you should be able to confirm it with the test procedure. Hope this helps and good luck to you.
Images (Click to enlarge)
Friday, November 18th, 2011 AT 5:37 PM