how should i approach it.

 

Check to see if the diaphram is working. You can see/feel it move with vaccuum applied. Also the lower port on mine was severely clogged. I had to take it off and run a wire and carb cleaner throuh it. It finally opened up to the big pipe.
Finally the EGR module needed to be changed on mine. Its a dealer item and not expensive. This is what I had to do to pass smog anyways. My truck codes don't go nearly that high. Up to code 12 or something like that.
Good luck

 

Approach it quietly from behind & jump on it quickly with both feet...

 

Mine's doing the same thing now, intermittent, for a few months. I pull the EFI fuse momentarily(truck stopped) to clear it. When it stays on all the time, I'll investigate. EGR valve is in a lousy place...very difficult/impossible to see to service.