An electronic engine control system comprises a central microprocessor integrated circuit, a program memory integrated circuit, and a programmable read only memory integrated circuit. The central microprocessor integrated circuit carries out calculations used in controlling an event associated with the engine according to a basic program contained in the program memory integrated circuit. The programmable read only memory integrated circuit is programmed to tailor the basic program contained in the program memory integrated circuit for the particular engine with which the electronic control system is utilized.