254 6 PERFORMANCE DIAGNOSTICS
NOTE: When using the EST to do KOEO or KOER
diagnostic tests, Standard Test is always selected
and run first. If the ignition switch is no t cycled, the
Standard Test does not have to be run again.
4. From the KOER Diagnostics menu, select Low
Duty cycle from VGT Tests, and select Run to start
test:
Use the suggested toggle sequence below, to
check turbocharger operation from one duty cycle
to the ot her.
• Low to medium
• Medium to high
• Hightolow
• Low to high
To toggle between duty cycles, select one of the
two remaining duty cycles and select Run to start.
As the VGT duty cycle increases when toggled
through the low, medium, and high duty cycles,
the EBP and MAP values shou ld increa se in
relationship to the VGT duty cycle. Conversely,
when duty cycle is reduced, there should be a
reduction to the EBP and MAP values.
If the ECM does not receive a request from
the EST, after about 40 seconds, the test will
automa tically end and th e engine will return to
normal operation.
5. Record results on Diagnostics Form.
• Did EBP and MAP change for each transition?
— If yes, continue to the next diagnostic test.
— If no, turbocharger is suspect for lo w
power condition. See “Low Power
(Turbocharger Assembly and Actuator)”
in Section 4.
Possible Caus es
• Intake or exhaust leaks
• Intake or exhaust restrictions
• Plugged EBP tube assembly
• Biased MAP or EBP sensor
• Failed VGT actu ator
• Failed turbocharger
• Failed EGR control valve
EGES-270-1
Read all safety instructions in the "Safety Information" section of this manual before doing any proced ures.
Follow all warnings, cautions, and notes.
©August 2008 Navistar, Inc.
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