International VT 365 Service Manual page 44

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3. Microprocessor
The ECM microprocessor
instructions (control strategies) and value tables
(calibration parameters). The ECM compares stored
instructions and values with conditioned input values
to determine the correct operating strategy for all
engine operations.
Continuous calculations in the ECM occur at
two different levels or speeds:
Background.
• Foreground calculations are much faster than
background calculations and are normally more
critical for engine operation. Engine speed control
is an example.
• Background calculations are normally variables
that change at a slower rates.
temperature is an example.
Diagnostic Trouble Codes (DTCs) are generated by
the microprocessor, if inputs or conditions do not
comply with expected values.
Diagnostic strategies are also programmed into the
ECM. Some strategies monitor inputs continuously
and command the necessary outputs to achieve the
correct performance of the engine.
Microprocessor memory
The ECM microprocessor includes Read Only
Memory (ROM) and Random Access Memory (RAM).
ROM
ROM stores permanent information for calibration
tables and operating strategies. Permanently stored
information cannot be changed or lost by turning
the ignition switch to OFF or when ECM power is
interrupted. ROM includes the following:
• Vehicle configuration, modes of operation, and
options
• Engine Family Rating Code (EFRC)
• Engine warning and protection modes
RAM
RAM stores temporary information for current
conditions. Temporary information in RAM is lost
when the ignition switch is turned OFF or when ECM
Read all safety instructions in the "Safety Information" section of this manual before doing any procedures.
ENGINE SYSTEMS
power is interrupted. RAM information includes the
following:
stores operating
•
•
•
4. Actuator control
Foreground and The ECM controls the actuators by applying a low
level signal (low side driver) or a high level signal
(high side driver). When switched on, these drivers
complete a ground or power circuit to an actuator.
Actuators are controlled in three ways (determined by
the kind of actuator):
•
Engine
•
•
ECM Control of Engine Operation
The ECM controls engine operation with the following:
•
•
•
•
VGT control valve
The VGT control valve is an actuator mounted on
the top right side of the VGT. The VGT control valve,
a variable position valve, controls vane position in
the turbine housing. Vane position is controlled by
a switching voltage source in the ECM. The ground
circuit is supplied directly from battery ground at all
times.
Actuator control is achieved by setting a pulse width
modulated signal in response to engine speed,
desired fuel quantity, boost or exhaust back pressure
and altitude.
Exhaust Gas Recirculation (EGR) valve
The EGR valve controls the flow of exhaust gases into
the intake manifold.
The EGR drive module controls the DC motor in the
EGR valve.
EGES295-2
Follow all warnings, cautions, and notes.
© 2006 International Truck and Engine Corporation
Engine temperature
Engine rpm
Accelerator pedal position
A duty cycle (percent time on/off)
A controlled pulse width
Switched on or off
VGT control valve
EGR valve
IPR valve
Glow plug relay