DTC P0446 Evaporative Emission Control System Vent Control Circuit: Description

WARNING: This page is about a different car, the 2007 Toyota Prius. However, it is still accessible from the selected car via links, so may be relevant.

DTC DETECTION CONDITION

DTC	DTC Detection Condition	Trouble Area
P0446	One of the following condition is met while vehicle is driving (2 trip detection logic): No change in fuel tank pressure when purge VSV and pressure switching valve are opened No change in fuel tank pressure when fuel tank is depressurized to 740 mmHg and purge VSV is closed	Leak from EVAP system Pressure switching valve Purge VSV Vent valve Fuel tank pressure sensor

This DTC is designed to detect the pressure switching valve (3-way VSV) malfunction. If the malfunction is detected while the vehicle is running, the ECM illuminates the MIL and sets a DTC (2 detection logic). The pressure switching valve located on the canister is used to detect leakage from the bladder tank into the fuel tank. The valve opens during the bladder tank leak check. Then, the fuel tank's fuel vapor flows to the intake manifold without passing the canister.