how to test the EGR selenodi vacuum valve

that's not what that code means. you have an evap leak,a small one.OBD II Trouble Code P0442 indicates an Evaporative Emission Control System Leak Detected (small leak). It means your vehicle's engine control unit has detected a very small leak. The leak can be from a hole as small as 0.04" in diameter. The EVAP system is designed to prevent the release of gasoline vapors into the atmosphere. Fuel vapors are routed by hoses to a charcoal canister. The charcoal canister is responsible for storing gasoline vapors from the vehicle's fuel tank until the engine is ready to burn them through the combustion process. A code P0442 is usually caused by: 1. A loose or improperly affixed gas cap. 2. A non-EOM gas cap (one that is not fitted for your vehicle). 3. A small leak/hole in a fuel vapor hose. The first thing recommended doing when dealing with trouble code P0442, to remove and reinstall the gas cap, clear the trouble codes using an OBD scanner and driving for a few day to see if the codes come back. If the code returns spending a few dollars on a replacement gas cap (preferably one from the dealer) may be worth a shot. If the code still returns you will need to have the EVAP system inspected for leaks. EVAP hoses shrink with age, and EVAP hose clamps may get loose cause small leaks. There are many connections in the fuel system for fuel delivery, tank return, and vapor recovery. Each one has the potential to become a vapor or liquid leak. recommend tracing the entire EVAP system for loose, brittle, and/ or disconnected hoses.it may be easy to find or it may be hard to find.if the cap don't fix it,you might want to see about a smoke test if you don't want to fool with trying to find it.