Turn the ignition to (engine off) without touching the brake.
When a TCM is physically replaced—often alongside a new valve body or transmission assembly—it must be programmed or "calibrated" to function correctly. nissan-tcm
If your Nissan (like an Altima, Rogue, or Sentra) is shifting poorly, you can often perform a (also called a TCM Relearn) to clear its memory and allow it to adapt to current conditions. Turn the ignition to (engine off) without touching the brake