Last month my 2000 Ranger with the 2.5L and 5 speed threw a P0401 code alond with the gas cap code. I replaced the EGR valve and put my original gas cap back on. Last week the CEL came back on and the auto part store said it was EGR low flow.

I paid extra for the Motorcraft EGR valve, so I'm wondering if I got a bad one. What else can I look at in the system?

Thanks,

 

This is what I have on that code.......

A code P0401 most likely means one or more of the following has happened:

• The DPFE (differential pressure feedback EGR) sensor is faulty and needs to be replaced
• 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 & DPFE voltage. There should be a noticable 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)
• Replace the DPFE sensor (with a good quality / OEM one)
• Replace the EGR valve

 

Thanks, Now I have an idea on what to look at.

 

I would suspect a bad DPFE first and foremost.

 

Don't forget to put the EVR/vacuum switching valve on the suspect list, as the computer commands it to supply operating vacuum to the EGRs diaphragm to have the EGR valve to open.

So if the EVR isn't functioning properly, it'll mess with how the EGR valve operates.

If the EVR itself checks out, look to it's electrical connectors pins & sockets, for corrosion, bent pins, spread sockets, damaged wiring, or corrupt operating voltage from the computer.

More thoughts for your suspect list.
Let us know what you find.

 

Another vote for the DPFE.
I've had 3 go bad so far on my 98 2.5L.

 

Thanks for the additional input. It won't be until next week before I get a chance to troubleshoot this.