This manual covers the Iveco NEF series engines, specifically the F4BE, F4GE, F4CE, F4AE, F4HE, and F4DE variants. These internal combustion engines are engineered for robust performance in both vehicle and industrial applications. The NEF engine family encompasses models utilizing mechanical injection systems, such as the F4BE, F4GE, and F4CE, alongside common rail variants like the F4AE, F4HE, and F4DE, including the F4DE specifically designed for industrial use. Iveco engines are known for their reliable engineering and efficient operation, making them a trusted choice for demanding environments. The purpose of this workshop service and repair manual is to provide comprehensive guidance for the maintenance, repair, and technical understanding of the specified Iveco NEF engines. It includes detailed information on general procedures, maintenance schedules, overhaul instructions, technical specifications, and necessary tools. Safety guidelines are also provided to ensure proper and secure handling of the engine. This manual is an essential resource for owners, mechanics, and technicians seeking to maintain the optimal performance and longevity of their Iveco NEF series engines across all covered applications.