Manifold Pressure/Vacuum Sensor: Description and Operation

This sensor senses pressure change in the intake manifold and converts it into voltage change. It consists of a semiconductor type pressure converting element which converts a pressure change into an electrical change and an electronic circuit which amplifies and corrects the electric change.
The ECM sends a 5-volt reference voltage to the pressure sensor. As the manifold pressure changes, the electrical resistance of the sensor also changes.
By monitoring the sensor output voltage, ECM knows the manifold pressure change when EGR valve is operated and judges the EGR flow to be faulty when this pressure change is excessively large or small.