EGR insufficient flow code

2000 Century with P0401 code. EGR valve had high coil resistance so I replaced the valve and reset SES light. Worked for about two months then the SES light came back. I am now thinking carbon build up is my problem? what is the best way to clean the EGR port, throttle body and etc?

What size engine do you have? The passageways are slightly different on different engines. The best way is to remove the egr valve and clean the passageways with a soft brush like a gun brush after spraying them with throttle body cleaner. If the egr is attached to the intake phlenum then remove it and clean everything with throttle body cleaner and replace. It will work wonders.

I have the 3.1L engine. Today I took the intake hose from the air cleaner to the throttle body off to see inside the TB. Looked like a lot of carbon build up. Took the EGR valve off and tried to run a piece of wire through the EGR port into the TB. Never saw the wire come through. Does the EGR port run under the TB and enter from the bottom?

Will get som TB cleaner and work on cleaning things up tommarrow. What type of brush were you refering to (gun brush)? Do I need to remove the TB to clean it?

If I recall correctly the 3.1 EGR is connected to the intake phlenum. The wire would not have come through where you could see it. The gun brush is a brass wire brush that cleans gun bores. A 22 caliber or 25 caliber brush should do the job. You can get them at sporting goods store or Walmart. Spray the area with the throttle body cleaner and wait for it to dissolve the carbon then run the brush through it. I would remove the phlenum and the throttle body to make sure you don't get anything in the engine. Also clean the entire phlenum and the throttle body at the same time. It will improve performance and fuel economy. Just make sure to label parts as you take them off and put everything back on in the same order. Put the phlenum bolts back in the exact same holes. It has something with flow design. Good Luck and let me know if it corrects the problem.

Thanks for your help, I did not remove the throttle body or plenum, but I did pull the butterfly plate out to give me more room to work. Found a brass brush similar to a tooth brush and TB cleaner. The EGR port does enter the bottom of plenum just downstream of the TB. Mine was plugged solid. I also took the EGR valve itself apart. Found that the pintle was stuck as well. Put it all back together, cleared the code and drove about 100 miles without code reappearing. Hopefully the problem is solved. Thanks again.