DTC P0449: EVAP Vent Solenoid Control Circuit: Description

WARNING: This page is about a different car, the 2002 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.

The Evaporative Emission (EVAP) system is used to store fuel vapors as to reduce the amount of unburned fuel from escaping into the atmosphere. The function of the EVAP vent solenoid is solely for EVAP leak diagnostics. Outside air flows around the normally open valve (except during portions of the EVAP diagnostic test) through the EVAP canister to the fuel tank. This allows the fuel tank to be at atmospheric pressure around 101 kPa. The ECM controls the solenoid by supplying it ground whenever the EVAP system is not venting (during the EVAP leak diagnostic test). When the solenoid is commanded off (circuit not grounded), the voltage level at the ECM should be high (ignition voltage). When the solenoid is commanded on (circuit grounded), the voltage level at the ECM should be low. The ECM EVAP vent solenoid feedback circuit uses a pull-up voltage (2.6-4.6 volts), which allows the ECM to individually differentiate between an open, short to ground or short to voltage. DTC P0449 will set if the ECM detects an open EVAP vent solenoid control circuit when EVAP vent solenoid is commanded off with engine cranking/running.