This manual covers trucks equipped with the DDEC II Electronic Engine Control System, primarily produced in the early to mid-1990s. Known for its durable and high-quality commercial vehicles, these trucks were offered in various configurations for heavy-duty applications. The DDEC II system represented a significant advancement in engine management for its era, powering Detroit Diesel Series 60 engines ranging from 11.1L to 14.0L, typically producing between 250-500 horsepower. These trucks were designed for demanding vocational and over-the-road use, often paired with manual transmissions, though early automated systems could also be integrated.

This comprehensive wiring schematics manual provides essential, factory-level documentation for the DDEC II Electronic Engine Control System. It details the Engine Control Module (ECM) circuitry, sensor inputs, actuator outputs, power and ground distribution, and diagnostic connector interfaces. The manual includes detailed diagrams for critical engine functions such as fuel injection, ignition timing, and emissions control, as well as wiring for diagnostic ports and communication links. Its scope encompasses troubleshooting common wiring faults, identifying components through pinout diagrams, and verifying harness installations. This resource is invaluable for owners, mechanics, and technicians seeking to accurately diagnose and repair electrical issues within the DDEC II system, ensuring optimal performance and fleet uptime.