How do you fix P0401 in 2006 Ford Freestar?

Answer 1

P0401 code means insufficient EGR flow. The usual causes are:

1. The DPFE (differential pressure feedback EGR) sensor is faulty and needs to be replaced
2. There is a blockage in the EGR (tube), most likely carbon buildup
3. The EGR valve is defective or its ports are blocked with carbon.
4. The EGR valve may not be opening due to a lack of vacuum.

Just to help stop any others being confused. The Freestar's have an integral DPFE sensor in the EGR, which also includes the vacuum pressure regulator.

One benefit is you don't end up chasing code P0401 everywhere and replacing parts one at a time. The bad part, you have to replace the whole EGR (extremely comon on that van) due to 0401 error codes. Last one I installed was $126.

The good side though, you get a new DPFE, EGR and pressure regulator all at the same time and it's usually cheaper than buying the three parts separately, also quicker and easier to change as a single unit. Of course, make sure the two vacuum lines are not eroded or split (they have a plastic sheath and a moulded plug so they rarely fail). The EGR down tube has a small restrictor plate in it, but again it rarely clogs due to the heat of the exhaust that burns off deposits. Prob time for a new EGR I'm afraid.