A diagnostic module for technical diagnosis of field devices operated in an automation plant, a diagnostic system, a method, and a computer program are provided. The diagnostic module includes a local control device which has a field bus interface and is not web-enabled, a field device, which has a web-based interface, from a number of field devices, and a coupling module with a web interface for data communication with a cloud-based server and in particular for reception of an analysis message from the cloud-based server and with a conversion module for generation of a field bus message from the received analysis message and for transmission of the field bus message to the control device. The diagnostic module further includes a field bus for internal communication between the devices of the automation plant and for forwarding the generated field bus message to the control device for control of the automation plant.