Other Features; Detroit Diesel Electronic Control System - PREVOST H3-41 Manual

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 cost. 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
operations.
•
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) operate 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 the "Controls &
Instruments" chapter). Active and inactive
codes will flash respectively the STOP ENGINE
and the CHECK ENGINE indicators. Refer to
"Technical Information" chapter under "DDEC IV
Diagnostic Codes".
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