Truck has 67,000mi 5.4L
The code reads differential pressure sensor pressure too low.
I've done the following:
cleaned all the ports, tubes, EGR. None of it was dirty.
vac tested the EGR for leak down. EGR good.
small hoses were tested and good.
changed the diff press sensor and the EGR regulator with Ford parts.
After ck eng light re-set, the code re-sets in about 5 miles.

next plan is to check power and ground at the regulator and activate the regulator to see if the EGR comes on. (to ck the vac lines ect)

Is it possible that the computer is false coding? Maybe a knock sensor coding as a diff press sensor? I had a mass air flow on a 86'F150 cause a coolant sensor code one time.

Any help much appreciated!

 

I think only about one in fifty have actually had any EGR problems when that code comes. The problem is almost always the dpfe sensor. Check to see if there is any obstruction in the lines before and after the dpfe. I had chunks of what looked like corrosion way down in mine. Had to take em off and look through them at the sun before it came out. Worth a check. I am not a mechanic by any means but I am willing to help until the real knowledge gets off work and on here.

 

P1401 is a fault with the reading from the DPFE sensor (TOO HIGH, not too low- that's a p1400).

That meas a faulty sensor or the wiring to/from it.

If you have a scan tool that can read Mode 6 data, it's pretty easy to isolate the fault.

Steve

 

Sorry guys I need to correct that code reading, it's a P0401
"EGR Flow insufficient". It's been a while since I worked on this problem and I jumped before I looked! I'm just happy to communicate with people that have some knowledge on this.
I've cleaned every tube and port on the exhaust side and sensor tubes with compressed air and carb cleaner. Also I have changed the sensor with a new Ford part with matching serial number. I checked the tubes, EGR and sensor with a hand held vac pump. I back probed the sensor to ck with a volt meter, tied in a vac gauge and went for a drive to check operation but the system didn'
t operate at all, then ck engine light came on. No corrosion seen on any wiring harnesses. Sensor has power and ground. I'm not sure if the regulator has vac; the vac source has a multiple plug fitting so maybe some other component is leaking? All this stuff is really packed in the engine bay and it's hard to even get around the EGR. I'm not familiar with the "newer" scan tools. Can some of the tools do snap shot recording and live data desplays on my Ford?

'Thanks.