in - service diagnostic testing of containers with a climate control system used in intermodal freight transport includes automatically testing the functioning of the climate control system at a possibly pre - scheduled time which may depend on the period of time since the latest pre - trip inspection . according to the invention in - service diagnostic testing is performed with cargo in the container during transportation from origin to destination at a suitable time before expected arrival to the destination so that the approval resulting from the in - service diagnostic testing is fresh and up - to - date . results of the in - service diagnostic testing are transmitted wirelessly to a receiver at a central facility where managing and allocating a large number of containers to individual transport tasks is performed , and containers which have not passed the in - service diagnostic testing can be taken out of service for maintenance and repair .