Vane sweep in the Ford 6.0L was developed to help with the turbo stiction. Some signs of your vanes sticking is lack of power, delayed/erratic shifts, excessive popping through intake, black/white smoke. It acts like a turbo failure, which it kind of is, but in this case the only thing that fails is the vanes stick due to corrosion. Ford updated turbo design and as a last resort, applied the vane sweep strategy.
The PCM commands the variable geometry turbo actuator duty cycle from 15% to 85% in a step
pattern to help the turbo vanes achieve full movement.
Vane sweep occurs when the following conditions are present:
-The vehicle is stopped.
-The EGR is commanded off. The engine speed is less than 1,160 RPM.
-The engine oil temperature is greater than a calibrated value.
-Vane sweep repeats approximately every hour if the previous conditions still exist.
-Vane sweep may occur during scan tool commanded test functions.