An electronics housing for a high voltage system of a vehicle defines an interior region, and includes a connection header wall having a window. An optical proximity sensor is disposed within the interior region of the electronics housing, adjacent the window. A cover is removably attached to the electronics housing adjacent an exterior surface of the connection header wall. The cover is disposed over the window. The optical proximity sensor is operable to sense the presence of the cover through the window when the cover is attached to the electronics housing.