Check engine light came on, had check at dealer. It came back as dpfe sensor. Replaced sensor, within two months (2000mi)
light came back on, same problem. Replaced sensor, again. One week (500mi) light came on again. Everytime the light has come on gas mileage dropped about 3 miles per gallon. Any ideas what else could be causing this issue. Code come up 1400.

Year and engine size please. Then we can search the specific manual for your vehicle.

Sorry I thought I had put it down.
02 Sport trac 4.0 L SOHC