Number 8 Ball Check Valve (372)
WARNING: This page is about a different car, the 2008 Buick LaCrosse and 2008 Buick Allure. However, it is still accessible from the selected car via links, so may be relevant.
Located in the control valve body (300), is fed braking fluid from the manual valve (404) and directs it to the 2-3 shift valve (357).