Monitor Description

The ECM detects leakage of evaporative emissions from the bladder membrane by using the heated oxygen sensor and pressure switching valve. By opening the purge VSV and then closing the pressure switching valve, air in the outer tank is drawn into the intake manifold.

The ECM checks concentration of hydrocarbon (HC) molecules in the air drawn from the bladder membrane area. Also, the ECM checks the sensor output before and after closing the pressure switching valve. If there is change in the HC concentration when the pressure switching valve is opened or closed, the ECM will conclude that the bladder membrane is leaking. The ECM will illuminate the MIL and set a DTC.