98 Ford Explorer OBD Code 1405?

It's a code referring to the DPFE sensor. IT could be that one of the hoses are unplugged or broken or plugged or Egr tube coul be damaged.

Find your DPFE(about 1" by 3" little box. May be chrome or black plastic in color) To find it follow your exhaust manifold to the two small tubes that have short black hoses attached. These hoses lead(both of them) to the DPFE.

they should sell a spare one with evey ford truck! Keep it in the glove box! Like the ballast resistors for older mopars

Biker trash is correct.. the hose has a habit of burning off the sensor at times or the sensor will plug up causing the same code.. Best suggestion is to replace the sensor and both hoses with new Ford products (Autozone and others sell the sensor for cheaper, but they are aluminum and is basically the same ones Ford got away from due to corrosion issues..FOMOCOs newest are all plastic bodied that can handle the heat)

P1405 - DPFE SENSOR UPSTREAM HOSE OFF OR PLUGGED, From what I have seen of Explorer I would guess the upstream hose burned off the DPFE sensor. On the drivers side of the engine there is a tube coming up from the exhaust manifold to the EGR valve, there are 2 rubber hoses hooked to the tube, the top one is most likely burned off, often the port on the DPFE sensor will be melted also. This hose is a special silicon hose that your local Ford dealer should have in stock.