A vent solenoid automatically closes the fuel tank vent to prevent outside air from entering the EVAP system during an automobile emissions test. EVAP is short for the Evaporative Emissions System.
The EVAP system, including the vent solenoid, is found under the vehicle near the rear wheels. A check engine light or a failed emissions test is usually the first sign of a vent solenoid problem. Diagnostic codes P0440 through P0449 are the most common codes for EVAP system problems. Common problems that may trigger the codes are leaks, dirt, debris and faulty sensors or components. Additionally, a fuel tank that is hard to fill may indicate a solenoid problem.