P0402 EGR code on 2001 Expedition with 4.6L engine

Question:

This code P0402 -EGR flow high, came on the other day on my vehicle and when I introduced vacuum to the egr valve port at idle, the engine quit which tells me that the valve is OK. The engine seems to run OK except this nagging light so I reset the code but it came back. Is there a common fix for this code?

ATS Adviser:

There is a common fix for this and most of the time it is to replace the DPFE sensor. This sensor looks like a small box with 2 ports coming from the exhaust. The sensor is located between the valve cove and throttle body with tubes running from it. This sensor measures the exhaust back pressure when the EGR valve is activated. The passages (tubes) for this sensor can get cracked and leak to trip the code but there has been a lot of failure on the sensor itself. Also, if the tube has a build up of carbon and restrict the flow, the code can be set too. To check, measure the signal voltage of the sensor using a wiring diagram. Max reading is about 0.9 volt and any reading higher means you have to replace the sensor.

ATS Tip:

Wiring diagram is available at ATS if you are a member.