Is the engine pinging/detonating? If not you'll be okay a problem with the EGR system will increase Nox-oxides of nitrogen due to high combustion chamber temperature over 2500F deg

A code P0401 most likely means one or more of the following has happened
There is a blockage in the EGR (tube), most likely carbon buildup
The EGR valve is faulty
The EGR valve may not be opening due to a lack of vaccuum
Possible Solutions
In fixing this code, it is quite common for people to just replace the EGR valve only to have the OBD code return. The EGR valve is not always the culprit.
Use a vacuum pump and pull the EGR valve open while monitoring engine RPM's,There should be a noticeable difference in RPM's with the EGR open
Clean out the EGR valve and/or tubing to remove deposits
Check the voltage at the DPFE, compare to specified values (refer to a repair manual for your specific model)

Answered by rasmataz
68 questions asked

P0401 IS AN EGR FLOW

Exhaust Gas Recirculation (EGR) Valve Position Sensor Located On top right rear of engine

may have to remove and clean its passages

Answered by BMRFIXIT (expert)
19,736 answers provided