Questions and Answers

Ford Windstar DTC P0401 Q. Hi Vince, have a 1999 Ford Windstar with the following code; P0401 EGR Flow Insufficient Detected. So I started to troubleshoot my EGR system. The first thing I did was remove the vacuum to the EGR valve and while the vehicle was idling I applied vacuum to the EGR valve and the car stalled. For the time being I am assuming that the EGR valve works and the ports are relatively clear.

I then wanted to check the EVR but it was at the back of the engine and it was cold so I moved on. I started to look at the DPFE. I am no too sure how this sensor works but I think if it senses a difference in pressure from it's two inputs then this would indicate that the EGR valve is opened.

If the sensor detects equal pressure then the valve is closed, so I believe. At cold it should read less than 1 volt and between 4 and 6 volts at hot. This is from my Haynes. For some reason mine reads about 4.67 volts at cold and remains that way. I was not able to take it for a drive to fully warm up but I did let it warm up in the driveway and it never changed.

I applied vacuum to the EGR and the car idled roughly, EGR open, and I monitored the voltage, again 4.67 volts. As an experiment I disconnected the two exhaust inputs and measured the signal voltage. Again it read 4.67 volts. I assumed that this is equal pressure on both inputs, atmospheric, and should be the equivalent to no flow through the EGR.

What troubles me the most is that I would have assumed I would be getting an error that indicates too much flow and not too little since the sensor thinks the EGR is open all the time. Of course it could be that 4.67 volts is not high enough of a reading for a fully open EGR valve, but then 4.67 is certainly high for a closed valve.

A. I would remove the DPFE and verify that it is clean and free of contaminants inside. Check the reference voltage to the harness connector verify that it is equivalent to battery voltage. Reconnect the DPFE and check the output voltage, if it is still not changing you will have to replace the DPFE.

Additionally, it is always a good idea to clean the EGR valve pintle and port and lubricate the actuator shaft with some silicone or spray lube of your choice.