An interconnect device is disclosed for detecting whether an vehicle on-board diagnostics (OBD) data port includes a blocking diode or equivalent. that prevents back feeding of power through the OBD data port. If a diode is detected, the interconnect device alerts the user that the power cannot be back fed through the OBD II port connector. In such a condition, an alternate means is used to preserve the data mentioned above. Specifically, an alternative power supply can be connected directly to the battery cables that will be disconnected from the battery, for example, by way of battery clamps. In this way the alternative power supply is used to preserve the data until a new battery is reconnected to the vehicle battery cables. If a diode is not detected by the interconnect device, the interconnect device displays this fact to the user. The interconnect device includes circuitry for detecting and displaying whether a diode is connected in series with a power pin of the OBD II port connector. In addition, the interconnect device includes an OBD II port connector on one end connected by way of a cable to a connector, such as a cigarette lighter connector or hardwired directly to an alternate power supply.