A system, method, and battery control module for detecting negative contactor status of a battery, such as a high voltage vehicle battery, is disclosed. The method includes applying a constant current to a bipolar transistor element having a base, an emitter, and a collector, wherein the base is electrically connected to a first resistor and an analog-to-digital converter, the collector being electrically connected to a second resistor and a diode. A collected current is delivered by the collector, and the method includes injecting the collected current through the second resistor and the diode and into a negative contactor of a battery. The method also includes determining a resistance across the negative contactor of the battery. The system may include a battery having a negative contactor, the negative contactor having a switch side, and a battery control module in communication with the battery.