Abstract: Removable devices and systems for operating the four wheel drive (4WD) system of a tow vehicle having an electronically controllable part time 4WD system including a selectable 4WD low range mode are described. The removable device may comprise a first interface for coupling the removable device to a selector, the selector providing an indication of a desired operating mode for the 4WD system; a second interface for coupling the removable device to a controller-area network bus of the tow vehicle; a memory storing vehicle control codes; and at least one controller communicatively coupled to both the first interface and the second interface. The removable device, and system, may allow a vehicle operator to operate the tow vehicle in two-wheel drive low range mode.