A control device for a device that can be networked, in particular for a water or air heating device, operated with liquid fuel, of a motor vehicle, in the form of a supplementary heater or an auxiliary heater. The control device has a client-specific data interface by which the control device can be connected to a client-specific data network, in particular to a data bus in a motor vehicle. In order to reduce the expense on the maker's part for programming, testing, and diagnosis for different client-specific data interfaces, the control device has an additional, maker-specific data interface constituted as a bidirectional wireless connection, of which the control device can be connected to a maker-specific data processing device for respective programming, testing or diagnosis.