###### Abstract
The maintenance knowledge and instructions library can also be expanded and updated, which leads to a continuous improvement in repair and operating times. The concepts of Industry 4.0, big data, and predictive maintenance (PdM) are closely related [19; 27; 28]. PdM relies on monitoring machinery in order to optimize maintenance tasks, so that repair tasks are only executed when it is strictly necessary. The main value of this system is the notification of abnormalities or failures in development, which allow the scheduling of maintenance tasks, and thus, the risks and costs of unexpected breakdowns are minimized, and the industry has a greater awareness of the possibility of optimizing the operation and maintenance of assets through data on their current status or forecasted status, on their operation, or the quality of the manufactured product. The relation of Industry 4.0 with maintenance departments is important due to aspects such as updating, efficiency, and monitoring, being important tools to take into account, and also due to the interaction capacities, and the information exchanged, between humans, machines, and facilities; favouring the construction of capacities which allow companies to adapt to changes. All this involves proper knowledge management in the philosophy of Industry 4.0 [29; 30; 31; 32]. For this reason, technicians who work in this activity need highly sophisticated technical and knowledge components, and the human factor is implicated highly in their performance, with a high degree of tacit knowledge; although in this activity, organizational factors, behaviour of materials, and failure, are also widely studied. Regarding the knowledge management process, it is not conducted in the same way, although in other departments of the company (marketing, commerce, development, communications, etc. ), it has begun to be introduced, as another benchmark of competitiveness and innovation [33; 34; 35; 36; 37]. Therefore, the starting point is the visualization of knowledge management as a strategic resource [38], in any approach aimed at the efficient development of a maintenance department, and therefore of the company itself. For this reason, it is important to define and extract the mechanisms of structural coordination, facilitators, and creation of knowledge [39], which occur in a maintenance organization, improving its operational processes [40; 41], and transmitting an improvement throughout the company, and with it a management of human resources towards the achievement of knowledge management [42] with a useful and productive purpose. This knowledge management process must be taken into account within the maintenance activity, which consists basically in the generation, coding, transfer, and use of knowledge [43; 44; 45]. This article shows the result of a study carried out among maintenance technicians of large companies, using qualitative research techniques, whose main objective was to define the relationship of knowledge management within maintenance activities, from the perspective of the technicians which operate in these departments, visualizing the strategic aspects that make knowledge management important in maintenance engineering, as well as extracting the fundamental barriers and facilitators that these technicians consider for the creation, transmission, and use of this strategic knowledge. The maintenance technicians, who participated in the study, work in different types of industries in Spain, although the activities done by technicians are similar (maintenance actions, troubleshooting, maneuvering actions for machines and industrial process equipment, and energy efficiency actions, etc.). All this can affect the companies, since part of the strategic knowledge is lost when a maintenance technicians the company. From the study an important difference was observed between the perception of registered knowledge (explicit), and the knowledge that maintenance technicians have (tacit knowledge).