Canister Purge Regulator Valve - Description and Operation - Page 2503
Canister Purge Control Valve: Description and Operation
PVS Valve
The PVS (ported vacuum switch) valve allows vacuum to open the purge control valve as the engine warms up. The purge control valve closes as soon
as the engine is turned off and vacuum drops off.
The evaporative emission system may be equipped with either a 2 or 4 port PVS. The 4 port PVS valve is actually two vacuum valves in one, and
performs the same function as two 2 port valves.