The engine-mounted ECM includes control logic to provide overall engine management. The ECM continuously performs self diagnostic checks and monitors other system components. System diagnostic checks are made at ignition-on and continue throughout all engine operating modes. See Figure 3-1.
The ECM contains an Electronically Erasable Programmable Read Only Memory (EEPROM). The EEPROM controls the basic engine functions such as rated speed and power, timing of fuel injection, engine governing, torque shaping, cold start logic, transient fuel delivery, diagnostics, and engine protection. The control logic determines duration and timing of fueling, that results in precise fuel delivery and improved fuel economy.
Engines with more than eight cylinders operate with multiple ECMs. One ECM is called the Master, while the others are referred to as Receivers. The Master ECM is the primary controller of the engine. It receives input from the various sensors, determines proper timing and communicates this information to the injectors that the Master ECM controls. The Master ECM sends this information to the Receiver ECM. The Receiver ECM instructs its injectors to operate in the same manner. Capability exists to enable independent operation of each portion of the engine in the unlikely event that the communications fail between the Master and Receiver ECMs.
Part numbers for DDEC III and IV ECMs are listed in Table 3-1.
