Pressure Feedback Exhaust Sensor: Description and Operation

Differential Pressure Feedback EGR (DPFE) Sensor:

PURPOSE
The Differential Pressure Feedback (DPFE) Sensor outputs a voltage proportional to the pressure drop across the metering orifice which is supplied to the Powertrain Control Module (PCM) as Exhaust Gas Recirculation (EGR) flow rate.

OPERATION

Exhaust Flow Rate Detection
THE DPFE receives the exhaust pressure signals through two hoses referred to as the downstream pressure hose (REF SIGNAL) and the upstream pressure hose (HI SIGNAL). As Exhaust Gases flow past the upstream pressure hose and through the metering orifice, a pressure drop is created and detected at the downstream hose.

Exhaust Gas Flow Rate Control
This pressure drop results in a reference signal used by the PCM to know the exhaust gas "flow rate". The PCM then commands the EGR Vacuum Regulator to vary the position of the EGR valve. By using the DPFE signal as a reference and the EGR valve as a "regulator," the PCM can more accurately assess and control the amount of exhaust gases flowing into the intake manifold.


CONSTRUCTION
The DPFE sensor is a ceramic capacitive type pressure Transducer.