A sensor for detecting leaked cooling fluid in a battery pack or container. The sensor is part of a sensor wire, where one end of the wire is electrically coupled to the positive terminal or the negative terminal of the battery pack and the other end of the wire is positioned at a location where the leaked cooling fluid may accumulate. A fault isolation detection circuit monitors a voltage output from the sensor and determines that there is a cooling fluid leak if the measured voltage potential is greater than a predetermined voltage threshold.