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Detroit Diesel Electronic Control/ DDEC System (Detroit Engines)

Electronic Control Module (ECM)

Figure 1.1 - ECM DDEC IV (Series 60)

#THE BASICS
The ECM can be considered the most important component of the DDEC system, as it controls the engine operation and acts as an interface with the other subsystems and devices, via the SAE J1587, J1922, or J1939 data links.

In these roles, the ECM adjusts engine speed and torque by transmitting output signals to the electronic unit injectors or electronic unit pumps via the Injector Harness and interacts with the other subsystems:
  • Monitoring system status
  • Transmitting engine status
  • Receiving sensor input
  • Receiving system requests
The ECM adjusts engine speed and torque after:
  • Receiving input signals, diagnostic information, and requests from sensors and other subsystems and devices
  • Conditioning input signals
  • Performing calculations
  • Determining output signals necessary to achieve operating goals
The ECM also monitors and reacts to various situations as detailed below:
  • Certain ambient conditions can result in fuel rate and timing adjustments to control smoke during starting
  • Certain barometric conditions can result in fuel rate and timing adjustments to compensate for altitude
  • Certain oil temperatures require changes to compensate for differences in oil viscosity, reducing fuel injection variation
  • Engine speed and cranking time is monitored to determine if crank inhibiting is necessary
  • Vehicle speed is monitored and compared to user settings and instantaneous preferences specified by input switches to meet cruise control requirements
  • Requirements for driven devices like PTOs, air compressors, and pumps are monitored and compared to user settings, monitored conditions, and instantaneous preferences specified by input switches to achieve in-cab or remotely controlled PTO operation requirements
The ECM also:
  • Performs self-checks and retains fault codes within its memory
  • Monitors operating conditions and either signals the user with a light or cuts back fuel in an attempt to control overtemperature and abnormal pressure conditions for engine protection
  • Monitors operations to signal the user of an impending service interval
  • Broadcasts operational and diagnostic information over the data link

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 1.2 below.
Figure 1.2 - ECM and Harness

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, which results in precise fuel delivery and improved fuel economy.


#ENGINE SENSOR HARNESS
The Engine Sensor Harness (ESH) is installed at the factory and is delivered connected to all engine sensors and the ECM. See Figure 1.3 below for an illustration of a Series 60 Construction and Industrial ESH.
Figure 1.3 - Series 60 Construction and Industrial ESH


#VEHICLE INTERFACE HARNESS
The OEM supplied Vehicle Interface Harness (VIH) connects the ECM to other vehicle systems as shown in the VIH illustrations. See Figure 1.4 below. Read More: DETROIT Wiring Diagrams.
Figure 1.4 - Typical Construction and Industrial VIH

#Pulse Width Modulated Port (PWM #1, 2, 4)
The output of this port is capable of providing 50 to 1000 Hz modulation between 0% and 100% duty cycle with a resolution of less than or equal to 0.1% duty cycle and an accuracy of less than or equal to 20 μsec.

#Digital Output Ports
The digital output ports are: 419, 509, 988, 555, 499, 563, 564, and 565. Wire numbers 419 and 509 are reserved for the CEL and SEL, respectively.

The digital output ports are capable of driving a #168 bulb (three candlepower lamp) in a 12 volt system or a # 313 bulb (three candlepower lamp) in a 24 volt system. See Figure 1.5 below.
Figure 1.5 - DDEC III/ IV Internal Digital Output Circuits

#Digital Input Ports
The digital input ports are: 451, 542, 528, 523, 541, 544, 543, 524, 531, 583, 545 and 979.

A DDEC IV digital input circuit may be seen in the next illustration (see Figure 1.6 below).
Figure 1.6 - DDEC IV Digital Input Circuits

#Switch Ground
Switch ground (circuit 953) must only be used to provide ground for DDEC components (i.e. digital inputs) and must be sourced directly from the negative battery or bus bar terminal.

#Ignition
The ignition source may be either 12 or 24 volts depending on the ECM configuration. The DDEC ignition must be an independent input sourced directly from the battery post via a 5 amp weatherproof blade type fuse, circuit breaker, or equivalent.


#INJECTOR HARNESS AND INJECTION SYSTEMS
The injector harnesses (see Figure 1.7 below) are installed at the factory and are delivered completely
connected to the injection units and the ECMs.
Figure 1.7 - Typical On-highway Injector Harness

#Electronic Unit Injectors
The Electronic Unit Injector (EUI) (see Figure 1.8 below) operates on the same basic principle as the Mechanical Unit Injector (MUI) which has been incorporated in Detroit Diesel engines for over fifty years.
Figure 1.8 - The Electronic Unit Injectors
The EUI uses a solenoid operated valve to control injection timing and metering. The source for high pressure fuel delivery is the cam/rocker arm system. Fuel injection begins when the solenoid valve is closed. Opening the solenoid valve ends injection. The duration of valve closure determines the quantity of fuel injected. Read More: Cylinder Cutout Test on DETROIT Engines using Detroit Diesel Diagnostic Link (DDDL).

#DATALINK CONNECTORS
The connectors used to connect the data links are a 6-pin Deutsch connector for the J1708/J1587 Data Link or a 9-pin Deutsch connector for the J1939/1708 Data Link. DDC recommends that the OEM-supplied Data Link Connector be conveniently positioned in a well protected location facilitating subsequent DDDL/DDR usage (i.e., reprogramming, diagnostics, etc). Read More: Diagnostic Port on Electronic Engine and Transmission.
Figure 1.9 - 9 Pin Data Link Connector
The SAE J1939 Data Link must be twisted nine turns per foot. The maximum length for the SAE J1939 Data Link is 130 ft (40m).
Figure 2.1 - 6 Pin Data Link Connector
The SAE J1708/J1587 Data Link must be twisted a minimum of 12 turns per foot. The maximum length for the SAE J1708/J1587 Data Link is 130 ft (40m).

#SENSORS
The DDEC IV system is designed to operate with several types of sensors as listed below:
  • Variable Reluctance - Used to monitor the crankshaft position and the engine speed.
  • Thermistor - Used to monitor temperatures.
  • Variable Capacitance - Used to monitor barometric air, manifold, oil gallery and optional pump pressures.
  • Variable Resistance (Potentiometer) -  Used to sense throttle position. The output should between 0.5 and 4.5 V
  • Switch - Used to signal coolant level, inlet air restriction, and oil level.
  • Magnetic Pickup - Used to sense vehicle speed, accumulate trip distance, and to use several vehicle features.
#Sensor Types
The sensors integrated into the Engine Sensor Harness are factory-installed. The sensors integrated into the Vehicle Interface Harness are installed by the OEM.
  • Air Temperature Sensor (ATS) and Charge Air Temperature Sensor - Senses air temperature for functions such as fan control and engine fueling.
  • Common Rail Fuel Pressure Sensor (CFPS) - Senses fuel pressure to warn of impending power loss and engine fueling.
  • Coolant Pressure Sensor (CPS) and Intercooler Coolant Pressure Sensor (ICPS) - Senses coolant pressure for functions such as engine protection.
  • Coolant Temperature Sensor (CTS) and Intercooler Coolant Temperature Sensor (ICTS) - Senses coolant temperature for functions such as engine protection, fan control and engine fueling.
  • Crankcase Pressure Sensor (CCPS) - Senses crankcase pressure for functions such as engine protection.
  • Fuel Restriction Sensor (FRS) - Senses fuel filter restriction to warn of the condition of the fuel filter for maintenance purposes.
  • Fuel Pressure Sensor (FPS) - Senses fuel pressure to warn of impending power loss and engine fueling.
  • Fuel Temperature Sensor (FTS) - Senses fuel temperature for functions such as engine fueling.
  • Oil Level Sensor (OLS) - Senses oil level for functions such as engine protection.
  • Oil Pressure Sensor (OPS) - Senses gallery oil pressure for functions such as engine protection.
  • Oil Temperature Sensor (OTS) - Senses oil temperature for functions such as reducing variation in fuel injection and fan control.
  • Synchronous Reference Sensor (SRS) - Indicates a specific cylinder in the firing order.
  • Timing Reference Sensor (TRS) - Senses crankshaft position and engine speed for functions such as fuel control strategy.
  • Turbo Boost Sensor (TBS) - Senses turbo boost for functions such as smoke control and engine protection.

#Engine Sensor Harness and Sensor Location
Figure 2.2 - Series 60 Engine


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