Leak Detection Sensor: Description and Operation

This sensor senses pressure difference between the fuel tank and atmosphere, 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 fuel tank pressure changes, the electrical resistance of the sensor also changes.
By monitoring the sensor output voltage, ECM knows the fuel tank pressure change.
From variation of this voltage signal, ECM diagnoses if there is an EVAP vapor leakage from the EVAP line and fuel tank related parts.