Ok, I have been using this site for quite some time and I must admit I have been a little selfish. However, I am going to give everyone my story on a po402 code. After reading several threads on the matter I: I have a 01' expy 4wd 5.4l automatic tranny w/ 69,000 mi. My wife came home, barely that is saying the truck was shuddering and not hardly starting and idling. I 2 footed it down to Autozone and had them check the code...po402 code egr has excessive flow. Well, after reading several threads I decided to bypass the egr valve and go directly to the DPFE sensor. Went down to Napa and used my firefighter discount and $50.00 later and about 20 minutes worth of work ( that included put tools back up.) The truck was running perfect again. I also went ahead and added some seafoam to help the carbon build-up through the brake booster and added the rest to the gas tank....so if you see that po 402 code I suggest that you take a look at that DPFE sensor first with a multi-meter if you have one or at least buy one put it on and see if it is a fix if not take it back and get a refund and start breaking down the EGR valve and throttle body to check for carbon deposits.

 

I have been having the same problem. I bring it in and the light will be on. this would go on for a week then turn off for a week, come on for 4 days and off for 1 week or 2. So its random. But now 3 out of the 4 were insufficient flow, and q out of the four were excessive.

I spoke to a few shops and they try to get you to have it replaced at your expense and their labor. Ford wanted to charge me $400 something dolars to diagnose and replace the parts.

I was told 9X out of 10 it would be that sensor. SO I am debating whether or not I should replace it myself and say *** them and take the chance.

Also, would this have anything to do with gas mileage being pretty bad. I have heard yes, and others have said no....

 

I just had the same problem and replace EGR and DPSE sensor and code came back. Then I Took the throttle body off. turn it upside down,on the back side of the throttle body there are two EGR ports.They are stopped up with carbon,Get a small screw drive and throttle body cleaner and clean the two ports out. Takes about 45 minutes to do.Won't cost anything but time. There is some youtube videos on cleaning EGR ports. Hope this helps.