what causes this to turn the check engine light on .it still drive the same and the gas mileage is the same, what sensor would cause it egr, tbs or other equipment need help.

 

P1405 DPFE Sensor Upstream Hose Off Or Plugged
most likely you need a new dpfe sensor and hoses. but if you are looking at the engine, on the left side of the throttle body i think in the back on top of the engine is the dpfe for your truck. if the hoses are rotted or ripped then replace them (motorcraft only). if the sensor is broken then you have to replace it with motorcraft part only. i'd recommend you do the hoses if you have to do the sensor.

 

wait! i lied, if its the new style dpfe sensor its where i said it was. if its the old style then its on the right side of the tb right in front of the egr.
this is the old style https://www.f150online.com/galleries...4889-92125.jpg
heres the new style https://www.f150online.com/galleries...026-160811.jpg

 

its a 2001 5.4 i assume its on the left side