97 F150 EGR Insufficient Flow - DTC P401 (EGR Vacuum Regulator solenoid)

Greetings,


I wanted to run my troubleshooting steps past some of the more
experienced. I have a 97 F150 4.6L throwing a P0401 (EGR insufficient
flow). I think I have a bad EGR Vacuum Regulator solenoid.


I've disconnected the green vacuum line from the EGR Vacuum Regulator
solenoid to the EGR valve and applied a slight vacuum to the EGR valve.
The engine RPMs down almost stalling. I'm guessing the EGR value is
okay. Reconnected.


Moving to the EGR Vacuum Regulator solenoid. After engine warmup, I
checked the voltage on the EGR Vacuum Regulator solenoid connector. It
showed 12-13vdc. I assume that means the EGR Vacuum Regulator solenoid
should be open.


Reconnected the plug to the EGR Vacuum Regulator solenoid and pulled
the green vacuum line off the EGR valve, put my finger over the end and
could feel a very slight pulsation.. no vacuum however. I lightly
tapped the EGR Vacuum regulator solenoid with no change. Reconnected.


Disconnected the white / green vacuum line combo at the bottom of the
EGR Vacuum Regulator solenoid. The white line had a solid vacuum on it.
Reconnected.


If I understand the diagrams correctly, the EGR Vacuum Regulator
solenoid should be open with 12vdc applied to the connector. This in
turn should apply a vacuum to the green vacuum like going to the EGR
valve.. resulting in the EGR valve opening.


Do I have a bad EGR Vacuum Regulator solenoid or should I move on to
the Differential Pressure Feedback EGR sensor?


Thanks in advance.


Jason