Hey folks, CEL question for you. I've got an error code P0401. Google tells me it's an issue with the DPFE sensor. I've replaced it, delete the error code and it stays off for about a day before it comes back. I've replaced the EGR valve itself, same thing happens. What the **** could this be? The only other thing I can think is the EGR valve control solenoid.
Thoughts?

 

P0401 is "insufficient EGR flow". There are a couple of causes for this. You do not have enough exhaust gases flowing back into the incoming air to the engine. The prime suspects are:

EGR Valve
Blocked EGR Passageways
EGR Control (No or Low Vacuum)
Faulty solenoid or wiring

You have replaced the EGR valve. The next thing to look at is the hoses to check for leaks or blockages. The last area is the solenoid and wiring.

 

My son's 1999 XLT did that. Replaced the DPFE, cleared the code and it came right back (in about a day). Pulled the EGR and checked it out (was working just fine). Replaced the metal tube from the exhaust manifold to EGR (because we trashed it getting it off. Ended up replacing the EVAP solenoid. Code stayed away. Not sure if that is your problem, but worth looking at.

 

Is this the part you're talking about? 2010 FORD RANGER 4.0L V6 Vapor Canister Purge Valve / Solenoid | RockAuto

Thanks for the suggestions guys, I appreciate your feedback.

 

That looks similar to his. 1999 vs. 2010 / 3.0L vs. 4.0L. I think his has 3 connectors for rubber tubing (vacuum, egr, vapor cannister).

 

P0401 "insufficient EGR flow" as Tsquare said

The DPFE sensor reads the pressure difference at TWO points in the exhaust system
DPFE = Delta(differential) Pressure FEedback

When engine is running the exhaust system will have a pressure inside that varies by RPM but will be the same if tested at TWO point.
If EGR Valve opens to let exhaust into intake then the pressure will change near the EGR Valve, but not as much farther away
So..........DPFE sensor has a hose connected close to EGR valve and a hose connected farther away, both on exhaust system, often on EGR tube.

P0401 "insufficient EGR flow" means that when the computer opens the EGR valve, using EGR vacuum solenoid, the DPFE sensor is not reporting a large enough Pressure change between the TWO hoses so computer "sees" insufficient EGR flow via the DPFE sensor.

Yes, this is often caused by old and failing DPFE sensor, but what if one of the DPFE hoses was cracked or clogged?
Same thing, no pressure change
Or if hoses were reversed
If EGR Valves exhaust tube were clogged up as well
P0401 means not enough pressure change at DPFE sensor

Yes, EGR vacuum solenoid also needs to be working or EGR valve never opens, so no pressure change.
You can test it with 9v battery or 12v from vehicle battery, apply voltage to the 2 connections and valve should click, there is no polarity, as long as you have + and - it will click if it is working.

What if there is no vacuum at the EGR Solenoid?
To test that have engine idling and THEN apply voltage to EGR solenoid, EGR Valve should open and engine should start to stumble and die if EGR Valve is open long enough, so that would mean it tested Good.
No change in idle means no vacuum or EGR valve is not getting it or not working

 

I changed the DPFE sensor. Then I was having problems with Idle, It wanted to take off while i was stoped at a red light. I changed the IAC valve, idle is fine now, but got a code P0401. Could the DPFE sensor be bad again!! HELP!!!