Symptom
Excessive low power on take-off or intermittent low power from drive cycle 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 the way out towards frame rail 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. Turn the ignition switch to ON. 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, the turbocharger or 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 intermittent, 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 step 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.
