Abstract: An electrical control system for vehicles has a plurality of separate control modules which communicate via a communication bus and an operational program is installed in each of the modules so that all modules contain programming for the functions of each module. A programming and diagnostic system including a PC and a program connects into the bus so as to download the program from one of the modules for generating, modifying and viewing program logic steps using ladder logic which is then converted back Into an operating program format for communication to the modules. In addition, the status of the inputs and outputs of the modules of the apparatus can be displayed and forced using the programming and diagnostic system.