DTC P0600: A/T Control (3.3L): Description
WARNING: This page is about a different car, the 2002 Nissan Xterra and 2002 Nissan Frontier. However, it is still accessible from the selected car via links, so may be relevant.
These circuits are used to control the smooth shifting up and down during hard acceleration or deceleration. Voltage signals are exchanged between ECM and Transmission Control Module (TCM).