EGR Modulator

EGR modulator is also known as backpressure transducer. EGR modulator is used to help regulate EGR action. Under low engine load (low exhaust backpressure), modulator will allow ported vacuum signal to bleed off to atmosphere, allowing less EGR action. Under high engine load, high exhaust backpressure causes modulator valve to close and allow full vacuum signal to EGR valve.