3 DIAGNOSTIC SOFTWARE OPERATION 83
With the VGT vanes still closed, the ECM commands
the EGR to open, and allows EBP t o stabilize. The
ECM monitors the EBP press ure and com pares this
pressure to the expected values; pressure is expected
to drop. If EBP pressure does not match expected
pressure, DTC 346 is set and the test is cancelled.
With the VGT still closed, the ECM then commands
the EGR to close , and allows EBP to stabilize . The
ECM monitors the EBP pressure and compares
this pressure to th e expected pressure; pressure
is expected to in crease. If EBP pressure does not
match expected pressure, DTC 346 is set and the
engine will return to normal operation.
If all pressures matched the expected pressures,
no DTC is set and the engine is returned to normal
operation.
VGT Test
NOTE: TheVGTtestcanonlybedonewiththe
EST; MasterDiagnostics® software is required. The
Standard test must be done before doing the VGT
test.
The VGT test is a manual test that allows the
technician to set the VGT duty to low, medium, or
high and inspect the exhaus t system for leaks.
NOTE: Monitor EBP and MAP as VGT duty cycles are
changed.
Figure 84 VGT session
1. With the engine running, select
D_KOER_AirManagement.ssn from the
open session file window and select OPEN to
open the session.
Figure 85 VGT Low Duty cycle test
2. Select Diagnostics from the menu bar.
3. Select Key-On Engine-Running Tests from the
drop down menu.
NOTE: When using t he EST to do KOEO or KOER
diagnostic tests, Standard test is always selected
and run fi rst. If the ignition switch is not cycled, the
Standard test does not have to be run again.
4. From the KOER Diagnostics menu, select Low
Duty Cycle from VGT, and selectRuntostarttest:
Use the suggested toggle sequence below, to
check turbocharger operation from one duty cycle
to the ot her.
• Low to medi um
• Medium to high
• Hightolow
• Low to high
If the ECM does not receive a request from the EST,
after about 40 seconds, the test will automatically end
and the engine w ill return to normal operation.
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.
To Next Page
Loading...
Need help?
General