i have a b18c with a p28/s200 obd 1 tuned and have had it for a long time no problems till other day im getting code 21 light not on code stored. so i found the flow chart to try to diag the problem as said .http://i859.photobucket.com/albums/ab152/yebabee/vt11.jpg
i even replace the wire going from the pcm to all the way to the connector still nothing. car dose not act up in any funny way just vtec inop. oh and i forgot to say i dont have a pressure switch
was wondering if maybe you have came across they same problem?