This manual covers the Hitachi EX120-5 Excavator, equipped with ISUZU A-6BG1TQA and A-6BG1 TQA01 engines. Designed for demanding operational environments, the EX120-5 is engineered for reliability and efficient performance in various construction and industrial applications. Its robust construction and advanced systems ensure durability and productivity, making it a trusted choice for professionals seeking dependable heavy machinery. This comprehensive service repair workshop manual provides detailed instructions, diagrams, illustrations, wiring schematics, and specifications essential for maintaining and repairing the Hitachi EX120-5 Excavator. It is structured into distinct sections covering operational principles, troubleshooting, circuit diagrams, harness information, and detailed workshop procedures for the upperstructure, undercarriage, front attachment, and engine. This manual serves as an indispensable resource for owners, mechanics, and technicians, enabling them to perform diagnostics, maintenance, and repairs with accuracy and confidence.