0401 is Insufficient EGR flow.
0402 is EXCESSIVE egr flow.
Those two are conflicting, thus I would look at the DPFE sensor (basically, it controls the EGR)
It is rare for an EGR to actually fail, much more common (though still not excessive) for the DPFE to fail first. Check the DPFE, then the EGR. I would recommend following Tony's suggestion of cleaning the TB and testing the EGR's functions either way. you'll need the TB to be cleaned either way if you have any significant mileage on the car at all.