when in TP, if com4 is the only option showing up when the cable is plugged in(and driver setup), then that should be the COM port being created by the cable.

when doing the tests, is this with the cable plugged into the computer, but not the vehicle? because the test SHOULD fail while connected to a vehicle, but should pass when disconnected from the vehicle. it isn't always that cut and dry though, cables that fail that test can work flawlessly during actual scanning.