82 3 DIAGNOSTIC SOFTWARE OPERATION
Air Management Test
Figure 83 Air Management diagnostic readout
The ECM commands the EGR valve to close. The
ECM then increases engine idle speed to 950 RPM
and commands the VGT vanes to fully open. The
ECM allows EBP to stabilize. The ECM monitors
the EBP pressure and compares this pressure to the
expected pressure; press ure is expected to drop. If
EBP pressure does not match expected pressure,
DTC 345 is set and the test is cancelled.
NOTE: Although commanding the EGR to close, it
may be stuck partially open, which would cause EBP
values to be lower than expected causing the test
to fail during the VGT portion of this test. If this is
suspected, the operation of the EGR valve should be
visually inspected using the Output State tests.
With the EGR still closed, th e ECM com mands the
VGT vanes to fully close. The ECM allows EBP to
stabilize. The ECM mo nitors the E BP pressure and
compares this pressure to theexpectedpressure;
pressure is expected to increase. If EBP pressure
does not match expected pressure, DTC 345 is set
and the test is cancelled.
With the EGR still closed, the ECM commands the
VGT vanes to fully open. The ECM allows EBP
to stabilize. The ECM monitors EBP pressure a nd
compares this pressure to the expected pressure;
pressure is expected to drop. If EBP pressure does
not m atch expected pressure, DTC 345 is set and the
test is cancelled.
If all pressures matched the expected pressures, no
DTC is set and the test will continue for EGR.
With the EGR still closed, the ECM increases engine
RPM to 1200 rpm and commands the VGT vanes
to fully close. Th e ECM allows EBP to stabilize.
The ECM monitors the EBP pressure and compares
this pres sure to the expected pressure; pressure
is expected to increase. If EBP pressure does not
match expected pressure, DTC 346 is set and the
test is cancelled.
EGES-270-1
Read all safety instructions in the "Safety Information" section of this manual before doing any procedures.
Follow all warnings, cautions, and notes.
© August 2008 Navistar, Inc.
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