Code P0401

Exhaust gas recirculation insufficient. I changed vacuum switch. DPGE sensor, tested EGR valve and when it’s opened by vacuum tester it shuts engine down at idle immediately. I checked voltage at switch and tested ground circuit monitoring it via multimeter. I see the analog voltage increase with RPM’s. It’s a grounding circuit. I blew air into hoses at dpfe sensor and air flows back to EGR tube both. Still getting fault. Racking my brain. Is there a flow sensor that possibly can throw this code? If so where is it?

Yes, I’m leaning on tubes carbonized but there’s enough flow to shut off the engine at idle when adding vacuum to EGR valve. Not sure why this time around it didn’t shut off on the test just shaking the engine real bad. This video is power braking when ramping up idle and you can see the voltage follows.

Here’s video of test to EGR valve. This time doesn’t shut off. Maybe carbon building worsened?

I would like to thank you for the fast response. FYI, I had purchased a new PDFE and Valve switch for EGR through Amazon. The switch bypassed so I sent it back and they sent me another one bypassing. Fortunately my electric valve is still working. I have no faith in cheap automotive electrical parts through Amazon anymore. So tonight I replaced the PDFE sensor from O’Reilly automotive parts. Tossed away the Amazon junk! Guess what? The EGR system is functioning perfectly and no check engine light has come back on. The voltages on my meter are running low to mid 3 volts so it’s running efficiently. Cheap parts have cost me a lot of anxiety. Thank you for your support on this site.