2-3 Shift Valve (357)
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.
When shifted, allows D4 fluid to enter the 3rd passage to stroke the 2-3 accumulator piston (136) and apply the 3rd clutch. The 2-3 shift valve also allows input clutch apply fluid to exhaust into the D3 passage and out at the manual valve (404). And provides 2-3 off signal fluid to the 1-2 shift valve.