Insufficient EGR P0401 code

On my 3L v6 (2001 XG), I'm getting a sporadic P0401 code set. Cleared it last Spring but now that cool temperatures are back it's been set again several times. Cleared it again a week ago -good for a week, now twice this
week it's been reset. It looks like it's set more often once the ambient temp is colder. Does this help pinpoint whether it's the EGR valve itself, solenoid, or sensors?? The workup in the manual seems involved especially as this problem seems sporadic. Thanks for any comments. BCinBC
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

This doesn't do much to rule out or pinpoint anything. Most failures are with the EGR solenoid or the vacuum control valve (called a vacuum switch in the parts catalog).
On the other hand, depending on the results of one simple test, you can rule out everything except these two components. If you can do that, you could do trial and error (the vacuum switch is the more frequent failure) or simply replace both components.
Your EGR system works as follows: The green-striped vacuum hose applies vacuum to the EGR valve and (through the vacuum control valve) the EGR solenoid. The yellow- striped hose runs to the other side of the EGR solenoid and vents back to the throttle body. When the EGR solenoid is open (its normal state), all vacuum returns to the engine via the yellow-striped hose. When the EGR solenoid is activated, it blocks the vent path, and vacuum (as limited by the control valve) is applied to the EGR valve, which should then open.
Here's my test-- you'll need a 10mm socket, an extension, a ratchet, and a pair of needlenose pliers. Remove the engine cover, start the engine, and pinch the yellow- striped hose shut near the throttle body. The engine should begin running very rough. Release the pliers. The engine should return to normal operation. If this all occurs as described, you've just verified the EGR valve is working properly, the EGR passage is clear, and that the vacuum hoses are all in place and routed properly. Your potential problems are the EGR solenoid and the vacuum control valve.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Thank you Hyundaitech. Yes, the EGR is good -car stumbled & stalled. I had given the vac control switch a tap or two & pulled the wiring off the solenoid. It looked clean so I firmly reseated it. Things have been good again for a week or so. BTW I took that silly plastic engine cover off & left it off years & years ago. BC
wrote:

This doesn't do much to rule out or pinpoint anything. Most failures are with the EGR solenoid or the vacuum control valve (called a vacuum switch in the parts catalog).
On the other hand, depending on the results of one simple test, you can rule out everything except these two components. If you can do that, you could do trial and error (the vacuum switch is the more frequent failure) or simply replace both components.
Your EGR system works as follows: The green-striped vacuum hose applies vacuum to the EGR valve and (through the vacuum control valve) the EGR solenoid. The yellow- striped hose runs to the other side of the EGR solenoid and vents back to the throttle body. When the EGR solenoid is open (its normal state), all vacuum returns to the engine via the yellow-striped hose. When the EGR solenoid is activated, it blocks the vent path, and vacuum (as limited by the control valve) is applied to the EGR valve, which should then open.
Here's my test-- you'll need a 10mm socket, an extension, a ratchet, and a pair of needlenose pliers. Remove the engine cover, start the engine, and pinch the yellow- striped hose shut near the throttle body. The engine should begin running very rough. Release the pliers. The engine should return to normal operation. If this all occurs as described, you've just verified the EGR valve is working properly, the EGR passage is clear, and that the vacuum hoses are all in place and routed properly. Your potential problems are the EGR solenoid and the vacuum control valve.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.