Manual Second Gear: Notes
WARNING: This page is about a different car, the 2007 Cadillac DTS. However, it is still accessible from the selected car via links, so may be relevant.
When the gear selector lever is moved to the Manual Second (D2) gear range, the manual valve moves and allows line pressure to enter the D21 fluid passage. The transmission reacts by shifting immediately into second gear range. The transmission is prevented from upshifting into either Third or Fourth gear.