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Back to Detroit Diesel Engine Information
DDEC I, DDEC II, and DDEC III & IV Schematics
DDEC I controls the timing and amount of fuel injected into each cylinder. The system also monitors several engine functions using various sensors that send electrical signals to the main Electronic Control Module (ECM). The ECM uses this information to send a command pulse to the Electronic Distributor Unit (EDU). The EDU functions as the high current switching unit for actuation of the Electronic Unit Injector (EUI) solenoids. The ECM also has the ability to limit or shut down the engine completely (depending on option selection) in the case of damaging engine conditions, such as low oil pressure, low coolant level, or high oil temperature.
DDEC II also controls the timing and amount of fuel injected into each cylinder. The system also monitors several engine sensors that send electrical signals to the main ECM. Unlike DDEC I, the DDEC II ECM uses this information to actuate the EUI solenoids. DDEC II incorporates all of the control electronics into one engine mounted ECM instead of the ECM and EDU that are required in DDEC I. The ECM also has the ability to limit or shut down the engine completely (depending on option selection) in the case of damaging engine conditions, such as low oil pressure, low coolant level, or high oil temperature.
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.
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.
