Hydraulic Shuttle Valves
WARNING: This page is about a different car, the 2005 Dodge Stratus and 2005 Chrysler Sebring. However, it is still accessible from the selected car via links, so may be relevant.
Two hydraulic shuttle valves allow pressure and volume to return to the master cylinder reservoir when not consumed by the build and decay valves. These valves are necessary because the pump/motor supplies more volume than the system requires.
If the brakes are applied at anytime during a traction control cycle, the brake lamp switch triggers the ABM to switch off traction control.