The only "active" device in this adapter is the one way check valve. Basic operation can be checked like the old "PCV" valves........if you can blow air thru but not suck air it works or can't blow and can suck. What that may not tell us is if it is occasionally failing. They should be asking for people throwing codes to send their adapters back for testing. I suspect it is a quality issue on the valve. My install is doing fine and I only hand tightened the clamps with a nut driver and old arthritic hands!