US Patent 7778749 Adaptive diagnostic cable with relay

An apparatus and method are provided that allow a scan tool to communicate with a data link connector in a vehicle. A cable that can automatically multiplex its connections in order to make the appropriate connections between the scan tool and a data link connector based on a communication protocol of the vehicle under test. This allows the scan tool to communicate with the data link connector regardless of the pins being used by the communication protocol of the vehicle. The cable is also capable of switching between a signal ground and a chassis ground in order to provide the scan tool with a reference signal.