Repetitive DTS Code P1404

2001 Buick LeSabre, 3.8L V6
Have Installed 4 EGR Valves in a Row, still keeps Tripping this Code (Pintle Valve Stuck Open). Have Checked Wiring & that all "appears" fine. Each Time I installed each one, I reset the ECM, within 30 minutes the "Service Engine Soon" Idiot Light Came Back on. What else could be causing this? How to Diagnose? Is there a way to Bench Test These Linear Valves? Have Emissions Certification in My Area, and I'm running out of Time & Patience, LOL....

Code refers to the pintle being stuck open when the pcm has commanded it shut, make sure the passgae is not carboned up causing the pintle not to seat and the harness and connectors are ok. Then you should have a scan done with a bi-directional scanner that can command the egr to see the results, if commanded closed and it fail this command the engine would run rough and vacuum would drop off. Also see this link. http://service.gm.com/gmspo/mode6/pdf/2001/2001file4.pdf

Code refers to the pintle being stuck open when the pcm has commanded it shut, make sure the passgae is not carboned up causing the pintle not to seat and the harness and connectors are ok. Then you should have a scan done with a bi-directional scanner that can command the egr to see the results, if commanded closed and it fail this command the engine would run rough and vacuum would drop off. Also see this link. http://service.gm.com/gmspo/mode6/pdf/2001/2001file4.pdf
So Is there a Way to "Bench Test" These EGR Valves before I Junk Them?

They are pulse width modulated. you could power it up and then try grounding it, you will need a wiring diagram for this or check the harness for which wire is powered.