EGR Backpressure Transducer: Description and Operation

When exhaust back-pressure is relatively high, as during acceleration and some cruising conditions, exhaust back-pressure traveling through the metal tube overcomes spring tension on the diaphragm within the back-pressure transducer valve, and closes the valve atmospheric vent.

With the back-pressure transducer valve no longer vented to atmosphere, the vacuum signal now passes through the back-pressure transducer valve, and the EGR valve. When vacuum signals the EGR valve, exhaust gas recirculation commences.

When exhaust back-pressure is too low to overcome diaphragm spring tension, the vacuum signal is vented to atmosphere and does not pass through to the EGR valve. With no vacuum signal applied to the EGR valve, exhaust gas does not recirculate.