Double K-LINE Adapter
This adapter performs the same function as the switch on many K+DCAN cables. It bridges pin 7 and 8 on the 16pin OBD port to allow full communication to older generation BMW's.
Models such as E46, E53, E39, E38, etc require this to communicate with the rest of the control units. Please be advised, if your cable has a switch like the Pro-Cable, you do not need this adapter.
If your car is earlier than 2001 or has the round 20-pin port under the hood, you must use that port instead of the 16-pin port inside the car. You will need a 16pin to 20pin BMW adapter. Those adapters can be obtained from Amazon for fairly cheap.