Car Code P0400 came up; what steps should I take to repair this?

What is your question?

Engine light came on; used my unit to check the code, came up with P0400, NOx Gases, Exhaust Gas Recirculation "A" flow was what I looked up. It recommends that I use a Dynamometer unit to test. According to information received from website; EGR passages or cylinders may be plugged or restricted. What do you recommend as an "eay" fix, if I can do it myself. Thank you, Santos

What makes this problem better or worse?

When cold started

How long has your 2001 Mercedes-Benz E430 had this problem?

Onlly a couple of days, engine light is now off