Pressure Hold
WARNING: This page is about a different car, the 2008 Saturn Sky and 2008 Pontiac Solstice. However, it is still accessible from the selected car via links, so may be relevant.
The EBCM closes the inlet valve and keeps the outlet valve closed in order to isolate the system when wheel slip occurs. This holds the pressure steady on the brake so that the hydraulic pressure does not increase or decrease.