This service manual covers the Cummins ISX and QSX series engines, essential for heavy-duty applications. These engines are renowned for their robust performance, durability, and efficiency, making them a preferred choice for demanding commercial and industrial operations. Engineered for reliability and power, the ISX and QSX models are designed to meet stringent emission standards while delivering exceptional operational uptime. Their advanced technology ensures optimal fuel economy and sustained performance under challenging conditions, reflecting Cummins' commitment to engineering excellence. This comprehensive manual provides detailed information for the maintenance, repair, and troubleshooting of your Cummins ISX and QSX engines. It includes essential technical specifications, step-by-step procedures for routine maintenance and complex repairs, diagnostic guidance, and safety precautions. Whether you are an owner performing basic checks or a professional technician undertaking in-depth service, this manual serves as an indispensable resource to ensure your engine operates at peak performance and longevity.