I can't see why to be a difference for nanocom if it's plugged into the cable or with the cable into the OBD port cos i see no logic and i've pluigged mine in so several times without any problem but if there are instructions about that better follow them and forget about this test even though it would have been a good test... but if you have access to testbook wait untill it's plugged in maybe you get a fault code and then you are on the good track

