1999 f250 egr circuit code

I believe the motor is a 5.4 liter v8 and the ses light came on a little while back and when I had it read at advance the code said insufficient air flow in egr circuit. Is there something that can be removed and cleaned to correct this or maybe a hose is leaking or that needs replacing? Never seen this code on any other vehicles Ive ever driven before. Any certain part I should start looking at first and work my way down until I find the problem? The guy at advance said it probably wasnt the egr valve itself because it said "circuit". Is this a true statement?

Was the code P0401? If so, check the return voltage on the DPFE sensor. It should be around .6 to 1 volt with key on engine not running. Should have the same reading at idle. If voltage is out of range, replace DPFE sensor.