Aktech

You guys need to measure the engine vacuum. It should be about 17-22. If it is not u got a air leak. Spraying vac lines are hit and miss. Under the hood there is a sticker that show your vac lines that need to be tested. I test them with a golf tee and a hand vacuum pump. There are a few sensors that can be tested to but it sounds like a vac leak to me.

Aktech

I would get a manual for your truck and test the egr vac regulator solenoid,egr and DPF egr sensor. Is your DPF connection two or three wire connection?

pjohnson2882

Well with me there is another issue... Not sure if it is or could be related... After running truck to normal temp... Then shut it off... If I go to start it back up within say 15 mins.... It acts like it half doesn't want to start n sounds/ feels like its running on two cylinders.... I hold the gas pedal down and after a few seconds, it levels out n runs (for the most part) normal.. (2nd) after each thing fixed, I would clear the codes and drive it while watching fuel trims... After each fix the light would come on after about 40 miles... But yesterday, I changed the egr valve and cleared the codes and drive it... The fuel trims were pretty normal (as far as I can tell from what I've read)... And the mil light/codes didn't come up until about 150 miles of driving...just wondering if you think it could be more or something else besides or ontop of what you posted

Aktech

In your 40-150 miles how much elevation change was there? You still need to pull engine vac.

forayzor

As I've said already above, intake gaskets are EXTREMELY common on the 4.2

Aktech

Just finish testing. Replacing some thing with out finishing the testing is a waste of time and money.If the gasket fails the test than replace it. Just because it is common problem it may not be your problem.There are lot of things that will make a engine run lean or rich. And replacing parts don`t fix a bad wire or ground going to the sensor or actuator.

Taylor13

Aktech

My DPFE is a 3-pin connector. I went to O'Reilly's on Saturday to re-read my codes, which was P0401, and to have the code reset. I then drove home, removed the EGR and DPFE and cleaned both and the hoses between them. There was a little gunk in the tubes of the DPFE, but not totally blocked. I reinstalled both and took a drive and the SES light came back on almost immediately. The engine continues to idle extremely smooth, with no knocking/pinging or other performance issues since replacing the elbow off the PCV. I've cleaned the throttle housing, Idle Air Control and MAF. I've replaced the plugs and fuel filter. With the engine running so smooth now, will ignoring the P0401 code cause problems down the road? Is it possible the computer just can't monitor the data as accurately as it should on a 13 year old vehicle?

Aktech

I don't think 0401 would cause to much harm at all. I now think it is a intermitent problem and goes back to working. If the truck is running good while driving maybe, waiting for a complete failure will make it easier to find.

forayzor

Bad wire going to what sensor or actuator to cause both banks lean? He's already replaced almost every part that could cause these codes and a few that wouldn't. Clearly he does not have the knowledge or resources to properly diagnose the issue. I know what can cause an engine to run rich or lean, I've fixed more than you can count. 80-90% of lean codes on this engine is caused by the intake gaskets. This is proven by myself, and proven to be fixed on a large amount of vehicles.

Bad wires or grounds will not cause these codes. The only way to properly diagnose this concern is with your archaic vacuum gauge, or properly with a scan tool, such as Ford's IDS to monitor short and long term fuel trims while at idle and higher RPM. Most effective way is in morning after first startup, monitoring trims and spraying carb cleaner around gaskets. With heat they will swell, hence morning diag time. If gaskets are leaking, you will see short term fuel trims spike negative.

forayzor

How will he know when a complete failure occurs? It is a hard fault, code returned almost immediately. Clearly, a complete failure is present. Ignoring the issue is not a fix

DPFE sensor causes this code commonly, but I won't suggest to replace it, I'll just recommend he "finish testing."