Circuit/System Description
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.
When the engine controller requests the neutral locked turbine (NLT) feature, the transmission control module (TCM) commands the 3rd, 5th and reverse clutch and the 2-6 clutch to apply, which locks the turbine shaft. This provides a load to the engine and reduces the engine warm up time.