Vgt Circuit Operation - Navistar International DT 466 Diagnostic/Troubleshooting Manual

526 7 ELECTRONIC CONTROL SYSTEMS DIAGNOSTICS
Function
The VGT actuator is a control module that contains
a microchip and a DC motor.
is located below the turbocharger.
operates a DC motor which rotates a crank lever
controlling the vane position in the turbine housing.
The position of the vanes is based off the pulse width
modulated signal sent from the ECM.
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 (manifold air pressure)
• Exhaust back pressure and altitude

VGT Circuit Operation

Figure 499 VGT circuit diagram
The VGT actuator receives power at Pin 1, through the
12-pin connector Pin 10, from the ECM main power
relay Pin 87. Ground for the VGT actuator is supplied
at Pin 2, through the 12-pin connector Pin 4 from
battery ground. The ECM controls the VGT actuator
by sending a pulse width modulated signal from the
ECM, Pin X1-18 to the actuator harness connector Pin
3.
The VGT actuator is controlled by varying the
percentage of ON/OFF time of the VGT actuator
control signal to control module. A high duty cycle
Read all safety instructions in the "Safety Information" section of this manual before doing any procedures.
The VGT actuator
The microchip
indicates a high amount of exhaust back pressure is
being commanded. A low duty cycle indicates less
pressure being commanded.
Fault Detection / Management
When the engine is running, the ECM can detect if
exhaust back pressure equals the desired pressure.
When measured exhaust back pressure does not
equal the desired pressure, the ECM will ignore the
EBP sensor signal and use a preset value based on
engine operating conditions.
EGES-270-1
Follow all warnings, cautions, and notes.
© August 2008 Navistar, Inc.