Pressure Feedback Exhaust Sensor: Description and Operation

Engine Emission Control Component Location - 3.4L SHO Engine:

Description and Operation
The EGR system is a differential pressure feedback (DPFE) EGR system. Differential pressure feedback EGR is a subsonic closed loop EGR system. The differential pressure feedback EGR system:

^ monitors EGR flow rate by the pressure drop across the metering orifice.

^ uses an EGR backpressure transducer as the feedback device.

^ uses the EGR valve only as a pressure regulator, rather than a flow metering device.




^ controlled pressure is varied by the valve movement using vacuum output of the EGR vacuum regulator solenoid.

^ allows for a more accurate assessment of EGR flow requirements.

Construction
The DPFE sensor is a ceramic capacitive type pressure transducer that monitors the differential pressure across a metering orifice located in the orifice tube assembly.

The DPFE sensor receives this signal through two hoses referred to as the downstream pressure hose (REF SIGNAL) and upstream pressure hose (HI SIGNAL). The HI and REF Signals are marked on the DPFE Sensor housing for identification (note that the HI Signal uses a larger diameter hose). The DPFE sensor outputs a voltage proportional to the pressure drop across the metering orifice and supplies it to the PCM as EGR flow rate feedback.