A DPFE sensor is short for "delta pressure feedback of EGR" and monitors changes in the EGR system's pressure. The EGR, short for "exhaust gas recirculation," functions to suck back gases that have been exhausted by the engine to reburn them. This process reduces pollutants emitted by cars.
The DPFE sensor is connected to the EGR through two tubes. These tubes become pressurized when gas flows through the EGR at which point any difference in pressure is recorded by the DPFE. By measuring pressure differentials, the DPFE can calculate how much exhaust gas is currently in the system. A failure in the DPFE sensor usually results in improper data being processed.