The Quality Control (QC) Department of PT. Mitsubishi Krama Yudha Motors and Manufacturing (PT. MKM) is responsible for producing products which prioritizes safety, function, and government regulations. The QC Department establishes the quality characteristics of each components and specifications in the early stage of the production process. A stable process and capable of meeting specifications can enhance the quality and business development. The process improvement methodologies, like six-sigma, etc., can improve the capability of the process. When the process is highly capable with minimum variability, sometimes it may not sense to monitor the process using traditional control charts, it is unable to detect the non-conforming product. Therefore, modified control chart is needed and allow the process mean to vary over a small interval provided the fraction non-conforming is within a pre-specified value. This study uses the method of adding data period to avoid violating the normality distribution assumption. The result shows there are 73 of the 240 plotted point is outside the modified control limits.