Checked my 1995 Blazer 4.3L 170,000 miles code today and P0401 came up. I replaced the EGR valve, and the carbon build up in the head was ridiculous. I cleaned it as best as I could, and put the new EGR on. It was fine for about 20 miles, then the code came up again.

I read this site: OBD-II Trouble Code: P0401 Insufficient EGR Flow
and its mentioning a DPFE sensor. What and where is that on my blazer? Could the issue be something else? Thank you!

 

I'm thinking the 'Differential Pressure Feedback EGR' is part of the egr. Sorta like a MAP sensor.
It separate on some fords.. and usually only it {being clogged} and the Manifold tube cause egr problems.
But this is probably your problem
What you might give a try is to use choke cleaner far toward the exhaust as you can get, then Plug the intake side and start car and see how much blows out that port. Might wanna lay a shop rag so it dont blow everywhere.

Wanna blow out more? Put hand over tailpipe

 

Your 95 4.3L does not have a DPFE sensor, (rinky dink old technology). GM doesn't use them, too many problems with them. The flow chart you used is generic, try this one, it's straight out of the dealer issue shop manual for your engine: https://blazerforum.com/forum/diagno...plained-38683/