The GM MDI is the Global Diagnostic tool GM Global A vehicles. It's a small communication interface module that manages the transfer of data between a vehicle's on-board ECU network with an auxiliary CAN bus.
The GM MDI was introduced in the fall of 2007 for Pass-Thru programming. It can be used to perform Pass-Thru programming on all vehicles built since 1996 and into the future. The MDI has been replaced by the MDI 2 (Bosch) with provides increased capabilities.
Global A vehicles will require GM Global Diagnostic System 2 software running on a local PC device while the MDI is connected to the vehicle.
The MDI connects to the vehicle via the J1962 connector using a DLC cable. Connection between the MDI and the PC can be accomplished via USB cable or through a CAT5 cable, or wireless networks.