This Service Repair Manual covers Komatsu engines, specifically models S6D140-2, SA6D140-2, SAA6D140-2, SA6D140E-2, and SDA6D140E-2. These inline 6-cylinder, water-cooled engines, with a displacement of 15.24 L and bore/stroke of 140 mm x 165 mm, are known for their robust construction and reliability. They are designed for demanding applications and are utilized in various heavy-duty equipment, including bulldozers, wheel loaders, hydraulic excavators, dump trucks, motor graders, and generators. The engines are available in naturally aspirated or turbocharged configurations, providing a horsepower range of approximately 200-400 HP depending on the specific variant and application. The purpose of this manual is to provide comprehensive guidance for the maintenance, repair, and servicing of the specified Komatsu engines. It details essential procedures, including general information, engine structure and function, testing and adjustment, disassembly and assembly, maintenance standards, and repair and replacement of parts. The manual also includes troubleshooting guidance, electrical and hydraulic diagrams, photo illustrations, and schemes to assist owners, mechanics, and technicians in effectively maintaining the optimal performance and longevity of their equipment.