Navistar International DT 466 Diagnostic/Troubleshooting Manual page 299

7 ELECTRONIC CONTROL SYSTEMS DIAGNOSTICS
movement occurs when the crank lever in the control
module moves.
Exhaust gas flow can be regulated depending on
required exhaust back pressure for engine speed
and load. As demand for EBP increases, the ECM
increases the pulse-width modulation to the VGT
control module. When EBP demand decreases, the
ECM decreases the duty cycle to the control module.
Actuator control for the vane position is achieved by
setting a pulse width modulated signal from the ECM
in response to the following:
• Engine speed
• Desired fuel quantity
• Boost
• Exhaust back pressure and altitude
The Exhaust Gas Recirculation (EGR) system
controls the amount of exhaust gas being introduced
to the engine mixer duct by modulating the EGR
valve. The EGR actuator is located at the front of the
engine on the mixer duct.
The EGR drive module controls the EGR actuator and
is located on the left side of the engine on the ECM
and Injector Driver Module (IDM).
The ECM calculates the appropriate desired EGR
valve position in response to the changing engine
speed, fuel desired, operator demand, engine
operating temperatures, exhaust back pressure,
boost pressure and altitude. The ECM uses sensor
input from the following:
• Variable Geometry Turbocharger (VGT) actuator
• Accelerator Position Sensor (APS)
• EGR actuator with position sensors
• EGR drive module
• Exhaust Back Pressure (EBP) sensor
• Manifold Absolute Temperature (MAT) sensor
• Barometric Absolute Pressure (BAP) sensor
• Engine Coolant Temperature (ECT) sensor
• Engine Oil Temperature (EOT) sensor
• Manifold Absolute Pressure (MAP) sensor
Read all safety instructions in the "Safety Information" section of this manual before doing any procedures.
The EGR drive module provides feedback to
the ECM on the valve position.
module interprets the ECM command and sends the
command using three pulse width modulated signals
to the valve actuator.
The system is closed loop control using the EGR
position signals. The EGR drive module provides a 9
V supply and ground to the Integrated Circuit (IC) in
the motor of the valve. When the EGR drive module
directs the valve to move, the IC with three Hall effect
sensors provides the EGR drive module with the valve
position signals. The EGR drive module interprets the
three signals to determine valve position and sends
the information back to the ECM.
Fault Detection / Management
The ECM continuously monitors the Air Management
System (AMS). When the ECM detects a fault in the
any of the interdependent systems, the ECM will set
a DTC and illuminate the amber ENGINE lamp.
The Variable Geometry Turbocharger (VGT) is
continuously monitored by the ECM using the exhaust
back pressure and the VGT pulse-width modulated
signal's duty cycle. A DTC is logged when the ECM
determines that the duty cycle required to reach the
desired boost or exhaust back pressure is greater
or less than the ECM's pre-programmed expected
values.
The Exhaust Gas Recirculation (EGR) actuator is
continuously monitored by the EGR drive module.
When an EGR control error is detected, the EGR
drive module sends a message to the ECM, a DTC is
set, and the amber ENGINE lamp is illuminated. For
additional function and operational information, see
"EGR Actuator" (page 413).
AMS Diagnostic Trouble Codes (DTCs)
DTCs are read using the Electronic Service Tool (EST)
or by counting the flashes from the amber and red
ENGINE lamp.
NOTE: Before proceeding make sure all sensor,
injector and actuator electrical DTCs have been
repaired. Follow the procedures outlined in Section 6
or Performance Diagnostics form.
EGES-270-1
Follow all warnings, cautions, and notes.
© August 2008 Navistar, Inc.
295
The EGR drive