Abstract: A plurality of control systems mounted on a vehicle such as an automobile, and provided for different controlled objects are respectively made of control computers. These control computers are linked by a common data bus. These computers exclusively execute, for example, an engine control, a transmission control, a brake control, a suspension control, and a auto drive control. The data bus is further connected to a diagnosis computer. Each control computer detects a signal from the sensor provided corresponding to each controlled object, and outputs the detect signal to the data bus. Each control computer executes the logical operation for its control on the basis of its detect signal and various data transferred to the data bus. The diagnosis computer supervises an operating state of each control system on the basis of the data transferred to the data bus. When an abnormality is detected, the diagnosis computer stores this data in a large-capacity memory, and displays the abnormality.

Abstract: A data network system for a vehicle having a plurality of separate and distinct control computers carrying out a predetermined control function of the vehicle and a data communication line for communicating data among the control computers. One of the control computers determines the number of the other computers which are linked with the data communication line, and in response to that number a data transfer rate output from each of the control computers to the data communication line is determined.

Abstract: A case for accommodating an electronic circuit for an electronic control system mounted on a vehicle is formed of an electric conductor and is electrically isolated from the grounding terminal of the electronic circuit which is provided on a printed substrate. Further, the outer boundary of a signal line for signal transmission between the electronic circuit and external circuits or sensors of the case is connected to the case through capacitors, thus preventing the faulty actuation of the electronic control system which otherwise might be caused by the electromagnetic wave.