This document is printed from SPI². Not for RESALE
The ECM is sealed and the ECM needs no routine
adjustment or maintenance.
Engine Speed
The electronic controls determine the injection timing,
the amount of fuel that is delivered to the cylinders
and the intake manifold pressure if an electronically
controlled wastegate is installed. These decisions are
based on the actual conditions and the desired
conditions at any given time.
The ECM has software that compares the desired
engine speed to the actual engine speed. The actual
engine speed is determined through the crankshaft
speed/timing sensor and the camshaft speed/timing
sensor. If the desired engine speed is greater than
the actual engine speed, the ECM will instruct the
electronic unit injector to inject more fuel in order to
increase engine speed.
Timing Considerations
Once the ECM has determined the amount of fuel
that is required, the software must determine the
timing of the fuel injection. Fuel injection timing is
determined by the ECM after considering input from
the following components:
• Engine coolant temperature sensor
• The sensor for the intake manifold air temperature
• The sensor for the intake manifold pressure
• Oxygen sensor
At start-up, the ECM determines the TOP CENTER
position of the number 1 cylinder from the secondary
speed/timing sensor on the camshaft. The ECM
decides when fuel injection should occur relative to
the TOP CENTER position. The ECM optimizes
engine performance by control of each of the
electronic unit injectors so that the required amount of
fuel is injected at the precise point of the engine's
cycle. The electronic unit injectors are supplied high-
pressure fuel from the fuel manifold. The ECM also
provides the signal to the solenoid in the fuel injection
pump. The solenoid in the fuel injection pump
controls a valve in the fuel injection pump. This valve
controls the volume of fuel that enters the plungers.
By controlling the volume of fuel that enters the
plungers, this controls the pressure in the fuel
manifold. Fuel that is not required for the engine is
diverted away from the fuel injection pump back to
the fuel tank.
The ECM adjusts injection timing and fuel pressure
for the best engine performance, the best fuel
economy, and the best control of exhaust emissions.
The actual timing can be viewed with an electronic
service tool. Also, the desired timing can be viewed
with an electronic service tool.
Fuel Injection
The programmable software inside the ECM sets
certain limits on the amount of fuel that can be
injected.
The FRC Limit is a limit that is based on intake
manifold air pressure and engine rpm. The FRC Limit
is used to control the air/fuel ratio in order to control
the engines exhaust emissions. When the ECM
senses a higher intake manifold air pressure, the
ECM increases the FRC Limit. A higher intake
manifold air pressure indicates that there is more air
in the cylinder. When the ECM increases the FRC
Limit, the ECM allows more fuel into the cylinder.
The Rated Fuel Limit is a limit that is based on the
power rating of the engine and on the engine rpm.
The Rated Fuel Limit enables the engine power and
torque outputs to conform to the power and torque
curves of a specific engine model.
These limits are in the programmable software and
these limits cannot be changed.
The ECM controls the following characteristics:
• Boost pressure
• Operation of the NOx reduction system
Diagnostic Codes
When the ECM detects an electronic system
problem, the ECM generates a diagnostic code. Also,
the ECM logs the diagnostic code in order to indicate
the time of the problems occurrence. The ECM also
logs the number of occurrences of the problem.
Diagnostic codes are provided in order to indicate
that the ECM has detected an electrical problem or
an electronic problem with the engine control system.
In some cases, the engine performance can be
affected when the condition that is causing the code
exists.
If the operator indicates that a performance problem
occurs, the diagnostic code may indicate the cause of
the problem. Use a laptop computer to access the
diagnostic codes. The problem should then be
corrected.
Event Codes
Event Codes are used to indicate that the ECM has
detected an abnormal engine operating condition.
The ECM will log the occurrence of the event code.
This does not indicate an electrical malfunction or an
electronic malfunction. If the temperature of the
coolant in the engine is higher than the permitted
limit, then the ECM will detect the condition. The ECM
will then log an event code for the condition.
UENR0623 35
Engine Operation
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