The EGR system aims to limit the production of nitrogen oxide emissions by redirecting them to the upper engine inlet. In this way, they are mixed with the air-fuel charge. As a result, the fuel mixture is burned at low temperatures, and consequently, fuel chamber temperatures are reduced, achieving a reduction in NOx emissions.
The Ford manufacturer controls the EGR/DPFE system directly from the PCM. These use the EGR valve, an electronic vacuum regulator that is known as EVR, and an electronic Differential Pressure Feedback EGR Sensor (DPFE). This measures the EGR flow, and it is located inside a tube in the system. When the valve is open, a pressure differential is created across the orifice.
The P1405 OBD2 diagnostic code is a manufacturer-specific code. Its setting occurs when the Powertrain Control Module finds a negative exhaust flow during engine operation with the EGR (Exhaust Gas Recirculation) valve in the closed position. Although this code does not directly refer to an EGR valve problem, the PCM uses certain valve needle position data as a setting parameter for this code.