Shift Problem - no 2nd or OD

2000 Sephia Automatic: Transmission only uses 1st and third. In 'D' it will usually start in 3rd. Occasionally it will start in 1st and then shift to third. If you select 1st, it will start in 1st and shift to 3rd after you select 'D'. Disconnecting battery to reset code may improve 1st selection until OD light starts flashing again. Nieces car, it has been a few weeks since I drove it. Checked other threads and plan to have the codes checked at a local parts store.