The scientific paper presents an original contribution regarding the modelling of the automatic EOL (End of Line) testing process of the Electronic Control Units (ECU) in the production flow in the automotive industry, by implementing the parallel testing algorithm to reduce the processing time at the related process station. This modelling operation for optimization must be implemented without affecting the quality of the automated functional testing process and is necessary for the application of the Kanban method in the automotive production flow. The process modelling begins with the analysis of the traditional execution time for each ECU input or output pin and continues with the development of a parallel test algorithm in which the test time for a single ECU is substantially decreased. By reducing the processing time of a station in the production flow, in this case at the EOL test station, a significant improvement in the capacity of the assembly line is achieved, which translates into cost savings at the resource level. The last part of the paper highlights the results obtained from the modelling of the process in order to optimize it and presents our conclusions developed in this case study.