This manual covers the Hitachi EX120-5 Excavator, equipped with ISUZU A-6BG1TQA and A-6BG1 TQA01 engines. Designed for robust performance and reliability, the EX120-5 is engineered to meet the demanding requirements of various construction and operational tasks. Its construction emphasizes durability and efficiency, making it a dependable choice for heavy-duty applications. This comprehensive guide is intended to support owners and operators in understanding and maintaining their equipment. The purpose of this service manual is to provide detailed information for the maintenance, repair, and troubleshooting of the Hitachi EX120-5 Excavator. It includes technical manuals covering operational principles and troubleshooting, a workshop manual detailing general information, superstructure, undercarriage, front attachment, and engine systems, as well as circuit diagrams and harness information. With step-by-step instructions, detailed illustrations, and critical notes, this manual serves as an essential resource for both experienced technicians and do-it-yourself users to ensure optimal performance and longevity of the excavator.