I have a 2000 Expedition with 192,000 miles, am still getting the p0401 code. I am ready to pull my hair out with this one.



I have cleaned the EGR ports, plugged solid, I have replaced all the vacuum lines, I have replaced the DPFE Sensor(non Motorcraft), EGR Valve, the EGR Solenoid, have checked the hard lines as well. I have sprayed Starter fluid along engine to see if there is anything leaking, no change in idle speed at all. It went away for a while but came back with a vengeance since.



I have also had the P0443 code as well, changed the EVAP Canister Purge Control Solenoid, this code went away after that, and the P0401 returned.



I am stumped, the only thing I haven't changed is the evaporative canister, could this be the problem, other than the aggravating CEL light the truck runs great, I installed a new set of COP's a few weeks back and am averaging between 18-20 mpg's. Now if I can get this light to go away, I will be a happy camper.

 

What's the condition of the EGR tube coming up from the exhaust manifold? Could that also be plugged?

 

I took it off when I cleaned the EGR Ports, and blew though it but did not push anything through it, I will check it again though, if any other suggestions, I am all ears.

 

DPFE is the culprit (in my opinion). Even though you replaced it, I would check for cracked hoses etc leading up to that. Did you get a plastic or metal DPFE sensor? Other than that, it could be EGR Valve, but that SUX to change out! .

 

I will try to check the voltage on the sensor and see what the output is, also, I just changed the EGR valve a couple of weeks ago.
Thanks,
Greg

 

Oh, it is the plastic DPFE sensor

 

According to manual, here are the possible causes. It doesn't say anything about cleaning egr to throttle body ports, but this should be done first. Also, when it says vacuum supply, this could be anywhere! I have heard of some who have replaced hoses behind the battery and made this code go away.

Vacuum supply
EGR valve stuck closed
EGR valve leaks vacuum
EGR flow path restricted
VREF open on DPFE sensor
DPFE sensor downstream hose is off or plugged
DPFE sensor hoses are both off
DPFE sensor hoses are reversed
Damaged EGR orifice tube
Damaged EGRVR solenoid

You should get about 5.0 volts between VREF and SIG RTN with the Key On Engine Off.

GOOD LUCK!

 

Thanks again, will update when I finish.
Greg