WARNING: This page is about a different car, the 2018 Nissan Titan XD and 2018 Nissan Titan. However, it is still accessible from the selected car via links, so may be relevant.
Transfer control unit controls 4WD mode (2WD ↔ 4H ↔ 4LO) by input signals of each sensor and each switch, and it directs shifts from 4WD shift switch.