This manual covers the Hitachi EX120-5 Excavator, designed for robust performance and reliability in demanding operational environments. Featuring an ISUZU A-6BG1TQA or A-6BG1 TQA01 engine, this model exemplifies Hitachi's commitment to engineering excellence. Its construction prioritizes durability and efficiency, making it a dependable choice for various construction and industrial applications. The purpose of this comprehensive service manual is to provide detailed guidance for the maintenance and repair of the Hitachi EX120-5 Excavator. It encompasses operational principles, troubleshooting procedures, technical specifications, and detailed workshop instructions, including information on the upperstructure, undercarriage, front attachment, and engine. This resource is designed to assist owners, mechanics, and technicians in understanding and performing all necessary service and repair tasks, ensuring the longevity and optimal performance of the equipment.