Does anybody knows the meaning of trouble code P1400?

The code P1400 reads "DPFE Sensor Voltage Low" (Ford, Mazda). Often it's caused by a bad DPFE sensor or clogged EGR passages. DPFE stands for (Differential Pressure Feedback EGRI) I would clean the EGR valve which cost nothing. If that does not cure the problem, you may need to replace the DPFE sensor, which does cost, and it may not fix the problem. If you want to be sure you replace the correct part, then visit your local Ford dealer.

dpfe stands for delta pressure not differential.