97 E300D CEL and code problem
 

No problem as I was driving 175 miles home last wednesday, the cel came on with no change in function that I could feel or see. Got a free check at Auto Zone and two codes. One was P0400 and the other was P0120 I checked out the egr, and related areas, and found nada. No apparent leaks and the egr was opening and closing. Was not sure the intake flappers were clicking so I took it to a registered MB tech at a respectable non dealer MB garage. He hooked up the computer and confirmed that the flappers were stuck. He cleaned them up today and also replaced a vacuum line that was burnt, but not sure it was leaking. He had a residual Code of P1404 "AHR control". which his computer shows as egr related and got an explanation that the egr was binding. However, it was checked out and works well at 25,50 and 75 and 100%. So we were unable to solve the riddle, as his achronym book did not explain "AHR control". I have looked at the available OBDII codes and no such number is listed. I am supposed to return in a couple of days while he searches for more info on this code. Anyone have any ideas??? Any help appreciated. Could this code just be erased???

Problem solved. It was a fluke that disappeared after removing and reinstalling all the vacuum lines in the area. Sorry for the trouble.