P0401 relates to insufficient flow from EGR valve. This can be caused by a faulty EGR valve or a blocked EGR passage from the valve to the inlet manifold.
How to access and clean the EGR passages in the inlet manifold.
See picture below how the EGR valve looks like.
Please let us know how you get along.
Tuesday, October 12th, 2021 AT 9:04 AM