Shift Solenoid Valve - Mode B
WARNING: This page is about a different car, the 2010 GMC Sierra and 2010 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.
HD 234 clutch/B cooling feed fluid is routed to the shift solenoid valve - mode B where it is blocked by the valve in preparation for an upshift to third gear.