The DDEC III/IV ECM receives electronic inputs from sensors on the engine and vehicle, and uses the information to control engine operation. It computes fuel timing and fuel quantity based upon predetermined calibration tables in its memory. Fuel is delivered to the cylinders by the EUIs, which are cam-driven to provide the mechanical input for pressurization of the fuel. The ECM controls solenoid operated valves in the EUIs to provide precise fuel delivery. See Figure 5.
Portable equipment facilitates access to diagnostic capabilities of DDEC III/IV’s. The Diagnostic Data Reader (DDR) requests and receives engine data and diagnostic codes. This equipment provides many unique capabilities including cylinder cutout, printer output, and data snapshot. The DDR also provides limited programming capability.