Jim Grant's Tech Tips
'01 Ford Ranger 4x4, EGR Code Problems
Q: Im getting a code P0401 (EGR Flow Insufficient) on my 01 Ford Ranger. Ive replaced the EGR valve and vacuum sensor and the code keeps coming back!? I also checked for vacuum leaks and didnt find any.
- Michael C.
A: This is just another classic case of information being misinterpreted. The code youre reporting didnt tell you that the EGR valve was broken; all the computer was reporting was that the flow in the EGR system was low. This code can be set for an array of reasons and you could be replacing a lot of parts before you get it right. The easiest way to diagnose this code is with a computer scan tool. It can be diagnosed with a multimeter but is more time consuming. The flow rate of the EGR system is determined by a sensor called a Differential Pressure Feedback (DPF) EGR sensor. This sensor measures a difference in pressure across a metering orifice located in the supply tube to the EGR valve. As the EGR valve opens there will be a pressure change reported to the computer by this sensor. The greater the EGR flow the greater voltage signal to the computer. With a computer scan tool the voltage signal from the DPF sensor can be monitored and compared to values in a diagnostic flow chart. DPF sensors do fail, but you want to be sure that it is bad before you replace it. A DPF sensor doesnt leave you much change from a $100 bill and dont try to return it (as good or defective) after it has been plugged in and found not to be the fix for the problem. Youll likely be asked to prove that it is defective or you own it. Have a technician with the right training and diagnostic tools pin down the cause for your EGR code. Once you know whats broken you can perform the repairs yourself if you wish.