This service manual provides comprehensive information for the Nissan Forklift Internal Combustion 1F5 Series, including specific coverage for Gas/LPG TB42 engines and S6S and 4HK1 Diesel engines. It is designed to assist users of all skill levels, from novice owners to professional technicians, in understanding and performing necessary maintenance and repair procedures. The manual emphasizes the importance of routine, preventive maintenance to ensure the longevity and optimal performance of the forklift, ultimately saving time and money by avoiding premature failures and costly repairs. The scope of this manual encompasses critical vehicle systems, including the engine, drive unit, drive axle, brake system, steering system, hydraulic system, and load handling system. Detailed sections are dedicated to engine mechanics, cooling, fuel, and electrical systems, along with troubleshooting procedures, diagnostic tools, and specific error codes. For diesel engines, it includes detailed information on general procedures, disassembly, inspection, repair, reassembly, lubricating systems, and special tool lists. This manual serves as an essential resource for maintaining and repairing the specified Nissan Forklift models, ensuring safe and efficient operation.