This manual covers the Allison 3000 Series Vocational Models, an automatic transmission known for its robust engineering and reliability in demanding applications. Designed with electronic control and a torque converter, these transmissions typically feature five or six forward gears, offering efficient power delivery. Their versatility makes them a preferred choice across various vocational vehicle types. This troubleshooting manual provides comprehensive official information for the electronic systems and components of the Allison 3000 Series transmissions. It details systematic diagnostic procedures for fault codes and symptoms, focusing on common areas such as the Transmission Control Module, solenoids, sensors, and wiring harnesses. The manual is an essential resource for owners, mechanics, and technicians to effectively maintain and repair these advanced transmissions, ensuring optimal performance and longevity.