Abstract: A method replaces a controller, particularly a faulty and/or outmoded controller, in an onboard power supply system in a vehicle. The controller to be replaced is replaced by a functional and/or new controller. The controller to be replaced and the new controller are operated by incompatible operating software. In the method at least one software component is exported from a software development environment for the operating software of the controller to be replaced by a data processing apparatus. The software component is converted into a code, which can be imported into a software development environment for the operating software of the functional and/or new controller, by the data processing apparatus. The code is imported into the software development environment of the operating software of the functional and/or new controller by the data processing apparatus. The operating software for the new controller is produced on the basis of the imported code.