EVAP Vent Solenoid
An electronic valve that seals the evaporative emissions (EVAP) system to allow the vehicle's computer to perform leak checks.
The EVAP vent solenoid (or vent valve) is an electronically controlled valve that is part of the vehicle's Evaporative Emissions Control (EVAP) system. Usually located near the charcoal canister under the vehicle near the fuel tank, the vent solenoid is normally open, allowing fresh air to enter the charcoal canister to purge fuel vapors into the engine intake manifold during normal driving.
However, when the engine control module (ECM) performs a self-test of the EVAP system to check for fuel vapor leaks, it commands the vent solenoid to close. With the vent valve closed and the purge valve open, the system draws a vacuum on the fuel tank and charcoal canister, monitoring the pressure sensor to ensure the system holds the vacuum and has no leaks.
Because the vent solenoid is located underneath the vehicle, it is exposed to dirt, dust, water, and road salt, which can cause the valve to stick open or closed. A malfunctioning vent solenoid will trigger a check engine light, typically with codes like P0446 or P0455. In some cases, a stuck-open vent valve can also make it difficult to fill the fuel tank with gas. Replacing the solenoid is a common emissions system repair.