I had the same code a few years back on my 1999 3.8L. It turned out my DPFE sensor was bad. If you pop the hood and face the engine the dpfe sensor is right up front on the drivers side near the end of the valve cover. It is practically staring at you. Very easy to find. Pop the hoses off of the bottom and check to see if they are clogged. You can test the sensor yourself. If you have a Haynes manual it tells you how to do this in chapter 6 section 14 and 15(6-14;6-15). If you don't have a manual I can probably type it out for you.
If the sensor is bad. Then it is easy to replace yourself. Two bolts, two vaccuum lines, and a wiring harness. Just make sure you label which vac. line is which. Part will run you around $86. That is what it cost me 2 yrs ago. Dealer wanted $190 to do the job. Ford part number is F77Z-9J460-AB
Hope this helps,
-TR | 
