The Komatsu PC400-6 and PC400LC-6 excavators are robust machines engineered for demanding construction and earthmoving applications. Powered by the Komatsu SAA6D125E-2 diesel engine, these excavators deliver substantial power and torque, featuring a 19.88 L displacement and a rated output of 203 kW. Their design emphasizes reliability and performance, with a hydrostatic, two-speed transmission enabling efficient travel at speeds up to 5.5 km/h. The PC400-6 has an operating weight of 40,950 kg and a ground pressure of 0.92 kg/cm², while the PC400LC-6 weighs 41,550 kg with a ground pressure of 0.78 kg/cm², offering versatility for various ground conditions. This Full Service Repair Manual in English provides comprehensive guidance for the repair and maintenance of the Komatsu PC400-6 / PC400LC-6 excavators. It covers essential information, including detailed engine specifications for the Komatsu SAA6D125E-2, transmission system details, and machine dimensions. The manual also outlines critical maintenance procedures, such as lubrication capacities for engine oil, hydraulic tank, swing device, and final drives, along with recommended replacement intervals for engine oil, fuel, and air cleaner filters. Furthermore, it details performance specifications like maximum digging depth, reach, and height, along with standard bucket capacity, ensuring owners and technicians have the necessary knowledge to keep these excavators operating at peak efficiency.