A diagnostic system for a power distribution circuit including a line, neutral and ground may include a switch configured to electrically connect the line and neutral, a first sensor configured to sense a line to neutral electrical parameter, and a second sensor configured to sense a neutral to ground electrical parameter. The system may also include a processor configured to close the switch, to observe at least some of the sensed electrical parameters before and after the switch is closed, and to identify a fault condition in the line or neutral based on the observed electrical parameters.