Not getting any replies from the technical forum so I wil try here...

I failed emissions with high Nox, which is why I started to test the EGR system. The valve does not lift when reving the engine between 2K and 4K. However, I have functionally tested it to see if it would hold vacuum. It does lift when applying vacuum directly from the throttle body. The other time it works is when I disconnect the purge control solenoid valve, thus permanently sending an OFF signal and allowing vacuum to pull the valve open.

So why isn't the ECM turning the valve on and off on its own? I also verified continuity between the ECM and the EGR temp sensor and purge control solenoid valve. It's as if the valve is always in an ON state, which is cutting the vacuum to the EGR valve. Could a faulty engine coolant temperature sensor cause this permanent on state? What else tells the ECM to turn the solenoid valve OFF?

Thanks for your help.

what year is your car?

The first thing I do with any egr problem is to turn it on 100% and see if the motor starts running like crap.

Egr problems are most commonly caused by clogged ports. I've only seen 2 bad egr valves but I've cleaned a lot of intakes.

Removing it is the only experience I have with egr on old b13 sentras. I personally don't believe in it. I think it's there to break and make money.

It's easy to test those little vac solenoids. First you blow air through them, if it's stuck open, it's broke, then just hook 12 volts to it and see if it opens.

A few things I have learned about the EGR solenoid:
The default position of the solenoid is Off, which turns the EGR on.
The ECU commands power to the solenoid to turn off the EGR when the engine is cold (under 167F), or at WOTso if your coolant temp. is too low (this happened to me when I had a thermostat that was stuck open and the temp. never got over 160) the EGR doesn't open.