An electronic control system mounted on an automobile, such as a motor-assisted power steering system, includes a commanding unit for calculating a command value and a driving unit for driving an actuator according to the command value. The commanding unit and the driving unit are communicably connected to each other through a communication bus. The command value is calculated in response to an order to calculate sent from the driving unit and is transmitted to the driving unit. The driving unit detects abnormality or malfunction in the commanding unit by comparing the transmitted command value with data pre-stored in the driving unit. If a command value sent from one of the commanding units is found to be incorrect, the actuator is driven without using the incorrect command value.