This code indicates a failure in the CAN (Controller Area Network) which is a serial communication line for real time application. It is an on-vehicle multiplex communication line with high data communication speed and excellent error detection ability. According to the FSM, the ECU lost communication with the TCM. The code is saying: When ECU is not transmitting or receiving CAN communication signal of OBD (emission-related diagnosis) with TCM for 2 seconds or more.
It could be a problem with the cabling or the connectors on the ECU or the TCM. Check the connectors for tightness and insure there is no oxidation on the pins.