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 demanding operational requirements. Its construction emphasizes durability and efficiency, making it a dependable choice for various construction and excavation tasks. This comprehensive service resource is intended for owners and operators who value maintaining their equipment in optimal working condition. The purpose of this service manual is to provide detailed instructions for the maintenance, repair, and troubleshooting of the Hitachi EX120-5 Excavator. It is divided into three key volumes: Technical Manual (covering operational principles and troubleshooting), Circuit Diagram & Harness, and Workshop Manual. These sections offer in-depth guidance on system operation, component repair, electrical circuits, and general information, enabling both do-it-yourself enthusiasts and experienced technicians to effectively service the vehicle.