Circuit Description

The Evaporative Emission (EVAP) purge solenoid is used to control flow of fuel vapors from EVAP canister to intake manifold. EVAP purge solenoid is commanded on whenever EVAP system is in purge mode. Fuel vapors can be purged at anytime PCM is in closed-loop and vehicle is not in decel mode. PCM controls EVAP purge solenoid by controlling an internal driver that pulls the solenoid circuit to ground. EVAP purge solenoid circuit is monitored for low and high voltage faults. During one part of the EVAP system test, PCM will close the purge and vent solenoids. DTC will set when fuel tank pressure sensor indicates that pressure is lower than atmospheric (vacuum), indicating that EVAP purge solenoid is stuck open. EVAP purge solenoid resistance should be 19-31 ohms.