Turbocharger Vane Position Sensor
WARNING: This page is about a different car, the 2009 GMC Sierra, 2009 GMC Cab & Chassis Sierra, 2009 Chevrolet Silverado, and 2009 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
The ECM uses the turbocharger vane position sensor to monitor the TC vane angle. The voltage is low when the TC vanes are open, and high when the TC vanes are closed.