The successful BMW Group pursues worldwide a customer-oriented quality strategy, which demands for continuous improvement. The target of zero-defect production in the BMW plant in Steyr, being the world's largest engine production plant within the BMW Group, is essential. To reach the object of being the leading provider of premium products and premium services for individual mobility, the management of BMW Plant Steyr promotes an extraordinary quality assurance of its production. The appliance of the requalification with internal criteria of the BMW Group shall identify weaknesses within the mechanical production and assimilate an improvement process for error prevention. Each of the 14 production lines at the BMW plant in Steyr is subjected to requalification. In particular, former mistakes are being observed to avoid similar ones in the future. For increased quality work in the production process, potentials for improvement shall be discovered. First, this thesis examines the significance of quality work in the automotive industry. The methods and the tools applied for the quality assurance in the production process are outlined. Furthermore, the company BMW Group itself is described, especially the motor production plant in Steyr. The requirements and the goals as well as the concept of requalification, in which the audit as a method is used, are being explained. The structure of a requalification will be shown with a practical example treated in the BMW plant in Steyr, followed by the results of all 14 performed requalifications. Finally, the sustainability of the requalification in the production process is compared with the theoretical part and the significance for BMW Group plant Steyr is analyzed.