Other systems use a purge flow sensor connected to a vacuum hose between the purge solenoid and the intake manifold. The PCM monitors the signal from the sensor once per drive cycle to determine if there is vapor flow or no vapor flow through the solenoid to the intake manifold. Other EVAP systems have a vapor management valve connected in the vacuum hose between the canister and the intake manifold. The vapor management valve is a normally closed valve. The PCM operates the valve to control vapor flow from the canister to the intake manifold. The PCM also monitors the valve’s operation to determine if the EVAP system is purging vapors properly. If no leaks are present and the purge cycle is correct, the system has passed the test.