4 ENGIN E SY M PTOMS DIAGNOSTICS 139
Low Power (Turbocharger Assembly and
Actuator)
Symptom
Excessive low power on take-off or intermittent low
power from drive cy cle to drive cycle
Cause
• Electrical power or ground issue
• Inoperative turbocharger assembly
• Failed turbocharger actuator
Tools
• Digital Multimeter (DMM)
• Turbo Breakout Harness
• 12-pin Breakout Harness
Procedure
1. Turn the ignition switch to OFF.
a. Move turbocharger linkage through its full
range of motion by hand. Linkage should
move smoothly and not chatter or hesitate.
b. Do a bounce test by moving turbocharger
linkage all th e way out towards frame ra il
and let it go. Linkage should move towards
engine, bounce, and stay there.
• If linkage moves smoothly, do step 2.
• If linkage does not move smoothly,
remove turbocharger actuator and move
linkage through its full range of motion.
— If linkage moves smoothly, replace
turbocharger actuator.
— If linkage does not move smoothly,
replace turbocharger assembly.
2.TurntheignitionswitchtoON.Watch
turbocharger linkage during pre-cycle movement.
Linkage should move all the way out towards
frame rail, move all the way back in towards
engine, and move back out about half way.
Check pre-cycle three times with at least three
seconds of key-off time between tests. Linkage
should move through pre-cycle smoothly and not
chatter, vibrate, hesitate or slow down during
pre-cycle. Each pre-cycle should be completed
in less than one second.
NOTE: When pre-cycle is complete with key-on
engine-off, the linkage should not move by hand.
• If pre-cycle fails, do step 3.
• If pre -cycle passes, th e turboc ha rg er o r
actuator may not be cause of low power.
— Verify that all tests on Performance
Diagnostic form do not indicate another
cause.
— If the low power complaint is interm ittent,
and all tests on Performance Diagnostic
form do not indicate another cause, do
step 3.
3. Connect turbocharger breakout harness between
engine harness and actuator harness. Measure
voltage between actuator power and ground
terminals with key-on engine-off.
• If pre-cycle fails, and voltage is 10 V or more,
replace the actuator.
• If low power complaint is intermittent, and
voltage is 10 V or more, inspect turbocharger
power and ground wires for corroded or loose
connections.
— If power and ground wires are
properly connected, not corroded,
and performance diagnostic tests do not
indicate another cause of low power,
replace the actuator.
• If voltage is low, repair low voltage problem.
See “VGT Actuator” in Section 7 (page 524).
— Go to s tep 2 and test again.
NOTE: The turbocharger actuator can be tested
again with a known good power and ground
supplied directly through turbocharger actuator
breakout harness.
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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