I have been working on what at first seemed to be an EGR problem. I was getting the bad EGR code.

I have cleaned the EGR several times. Each time resetting the codes by unplugging the EGR before resetting. I have removed the tube between the EGR and TB and made sure all is clean up to the TB. At this point I thought, OK bad EGR. Put the new EGR on, reset fault codes. 8 miles latter I get the P0401 code now. What else can I check?

She did run better with the new EGR valve.

Thank you in advance!

2001 SE Bonneville 138K miles

8/20 Found this and it is helping. May have a bad EGR. Still working on it today.

http://easyautodiagnostics.com/gm/4.3L-5.0L-5.7L/egr-valve-tests-2