CHAPTER 4 : OTHER FEATURES
DETROIT DIESEL ELECTRONIC
CONTROL (DDEC) SYSTEM
DDEC is an advanced-technology electronic fuel
injection and control system for Detroit Diesel
engines. As an integral part of the engine, the
DDEC system provides a number of
performance features and driver benefits;
including improved fuel economy and
performance, reduced cold smoke and reduced
maintenance and repair costs. These
advantages are obtained by optimizing control of
the critical engine functions which affect fuel
economy, engine reliability and the performance
of the injectors.
Its major components include an Electronic
Control Module (ECM), Electronic Unit Injectors
(EUI), electronic throttle pedal and sensors. The
ECM, which provides central processing and
control of the DDEC system, contains the
following:
•
A microprocessor that continuously monitors
and analyzes the engine's performance
using sensors during engine operation;
•
Flash Random Access Memory (FRAM) that
stores ECM runtime software, which
contains engine control instructions;
•
Electrically Erasable, Programmable, Read-
Only Memory (EEPROM) that provides
instructions for basic engine control functions
such as rated speed and power, engine
governing, cold start logic and diagnostics
and an engine protection system.
The Electronic Unit Injectors (EUI) operates on a
principle similar to the mechanical unit injector
system. However, a solenoid operated control
valve performs the injection timing and metering
functions which make injector timing much
simpler and more precise.
DDEC provides the capability of quickly
diagnosing system malfunctions with a self-
diagnostic system. The self-diagnostic system
monitors all engine sensors and electronic
components and recognizes system faults and
other engine-related problems by providing the
technician with a diagnostic code. The DDEC
system will illuminate the dashboard CHECK
ENGINE and STOP ENGINE indicators which
are integral parts of the electronic diagnostic
system. These lights are designed to indicate a
problem and transmit a coded signal to the
technician to locate the defective component.
To facilitate troubleshooting and obtain pertinent
data logged in the ECM (Electronic Control
Module) memory, a Diagnostic Data Reader
(DDR) can be used (not supplied by
manufacturer). Plug the DDR into the receptacle
on the upper left wall in the driver's footwell. You
can also momentarily depress the STOP
ENGINE OVERRIDE switch on the L.H. lower
control panel (refer to "Controls & Instruments"
chapter 3). Active and inactive codes will flash
respectively the STOP ENGINE and the CHECK
ENGINE indicators. Refer to "Technical
Information" chapter 8 under "DDEC IV
Diagnostic Codes".
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