HOW DO YOU CHECK EXISTING VACUMN SWITCHING SOLENOID VALVE FOR EGR?

If it's a regular 2-wire solenoid, one wire will be hot with key on engine off. To test the circuit, connect a test light between the two wires with the solenoid disconnected. If it lights up the circuit's good. To test the solenoid, you will not need the key on so turn it off. first (this is off the car) connect an extra piece of vacuum tube to the side of the solenoid that's connected to the intake manifold and see if you can suck any air through it. If air passes, the solenoid is bad. If not, take two jumper wires and connect one lead to the side of the connector corresponding to the 12V wire on the car. Connect the other lead to the remaining post in the connector. Hook the 12V wire to the pos side of the battery. While listening to the solenoid, touch the remaining lead to the negative post on the battery. If the solenoid clicks, try to suck on the tube again. If air passes now, the solenoid is good. In my experience, most of these problems are related to loose pin connections inside the connector. On EGR solenoid problems, always check for carbon that may be clogging EGR ports in the manifold. You will need to remove the valve to do so. Good luck