This standard specifies a serial data network for control and communications on forestry or agriculturaltractors, mounted, semi-mounted, towed or self-propelled implements. Its purpose is to standardise themethod and format of transfer of data between sensor, actuators, control elements, information storage and display units whether mounted or part of the tractor, or any implements. This part of the standard, describes the standard diagnostic system specified for tractors and self-propelled implements.