Cheap fix for P0401 EGR Low Flow
Removed the 90 degree elbow going to the intake(throttlebody came out too because I didn't separate it from the elbow). There is one long port on the side of the elbow where the EGR mounts that then splts into two smaller ports inside the elbow. These two smaller ports get clogged with carbon soot. This stuff is nasty and thanks to the EPA it is being recycled back into your engine all the time. You have to act like a chimineysweep and get this gunk out. Lots of carb cleaner, old tooth brushes and a gun cleaning kit really helps(45 cal. works for the small ports). I also used the compressor to blow the trash out. You want to do a thorough job here. I only used two gaskets(EGR and 90 degree base gasket-didn't need throttlebody gasket because I never separated the throttlebody from the elbow). A couple of cans of carb cleaner. Total cost under $15. If you get P0401 after doing this cleaning job you can then go out and purchase the EGR or DPFE which are at least $50.00 each at discount auto parts stores. You can try cleaning the EGR valve and DPFE first before buying new ones, but be careful what solvents you use to flush the trash out so as not to damage the rubber diaphram in the EGR valve or the sensor in the DPFE.