
4 RENR5622
Troubleshooting Section
Troubleshooting Section
Electronic Troubleshooting
i02414590
System Overview
SMCS Code: 19
01-038; 1924
The engine is designed for electronic control of most
engine opera
ting functions. The electronic system
consists of an Electronic Control Module (ECM), the
wiring harness, switches, sensors, and fuel injectors.
TheengineEC
M receives information from the
sensors and the switches on the engine. The engine
ECM processes the information that is collected in
order to mak
e decisions on control of the engine. By
altering the fuel delivery with the fuel injectors, the
engine ECM controls the speed and the power that is
produced b
y the engine.
Electroni
cControls
Electronic Control Module
The ECM consists of two main components, the
control computer (hardware) and the flash file
(software
). The control computer consists of a
microprocessor and electronic circuitry. The flash file
contains the engine’s operational characteristics. The
operatin
g maps influence the engine’s performance.
Engine Governor
The engine ECM governs engine speed. The engine
ECM and the personality module work together by
controll
ing the amount of fuel that is delivered by
the injectors. Desired engine rpm is determined
by the throttle position sensor signal and certain
sensor r
eadings. Diagnostic codes may derate the
engine. Actual engine rpm is measured by the engine
speed/timing signal.
Fuel Injection
The engi
ne ECM controls the timing and the duration
of the fuel that is injected. The engine ECM varies the
signals to the fuel injectors. Fuel is injected only while
an inje
ctor solenoid is energized by a 105 volt signal
from the e ngine ECM. The timing of the injection
signal determines the engine timing. The length of
the inj
ection signal determines engine speed. By
controlling the timing and duration of the 105 volt
signal, the ECM controls the engine speed.
Injection timing depends on the following conditions:
desired engine
rpm and load. The ECM detects
the top center of each cylinder. The ECM sends an
injection signal at the desired time.
Cold Cylinder Cutout
During a cold s
tart or extended periods at low idle,
theengineECMwillautomaticallyturnoffoneunit
injectoratatimeinordertodetermineifthecylinder
is firing. If
the ECM determines that the cylinder is not
firing, the ECM turns off the unit injector. If the ECM
determines that the cylinder is firing, the ECM turns
on the unit in
jector. This strategy improves engine
starting. This strategy reduces the following: white
smoke, the use of ether injection, and warm-up time.
Cold Mode Operation
Cold mode co
ntrols fuel injection timing when the
engine is cold. When the engine is cold, controlling
the fuel injection timing reduces the possibility of
engine dam
age. When the engine is cold, controlling
the fuel injection timing helps minimize white smoke.
Cold mode i
s activated whenever the engine coolant
temperature is below 70 °C (158 °F). Cold mode
remains active until the engine coolant temperature
is warmer t
han 73 °C (163 °F).
FRC Limit
The flash file inside the engine ECM sets certain
limits on the amount of fuel that can be injected.
The FRC li
mitisalimitthatisbasedontheboost
pressure. The boost pressure is calculated as the
difference in pressure between atmospheric pressure
and turbo
charger outlet pressure. The FRC limit
is used to control the air/fuel ratio for control of
emissions. When the engine ECM senses a higher
boost pr
essure, the engine ECM increases the FRC
limit. A higher boost pressure indicates that there
is more air in the cylinder. When the engine ECM
increas
es the FRC limit, the engine ECM allows more
fuel into the cylinder.
Rated F
uel Position
The rated fuel position is a limit that is based on the
power r
ating of the engine. The rated fuel position
is similar to the rack stops and the torque spring
on a mechanically governed engine. The rated fuel
positi
on determines maximum power and torque
values for a specific engine family and a specific
rating. The rated fuel position is programmed into
the fl
ash file at the factory.