DTC P0600: Automatic Transmission Communication Line Fault: Description
WARNING: This page is about a different car, the 2002 Nissan Pathfinder and 2002 Infiniti QX4. However, it is still accessible from the selected car via links, so may be relevant.
Communication line (LAN) is used to control smooth shifting up and down of A/T during hard acceleration and deceleration. Pulse signals are exchanged between ECM and Transmission Control Module (TCM). After repair be sure to erase DTCs in TCM as well as ECM.