Dynamic Rear Proportioning
WARNING: This page is about a different car, the 2010 GMC Terrain and 2010 Chevrolet Equinox. However, it is still accessible from the selected car via links, so may be relevant.
The dynamic rear proportioning is a control system that replaces the mechanical proportioning valve. Under certain driving conditions the EBCM will reduce the rear wheel brake pressure by commanding the appropriate solenoid valves ON and OFF.