Controller Area Network (CAN) Bus The CAN bus is a high speed broadcast network connected between various vehicle ECUs. + COMMUNICATION DATA BUSES, DESCRIPTION AND OPERATION, Description. The CAN allows the fast exchange of data between ECU's every few microseconds. The bus comprises two wires which are identified as CAN high (Hand CAN low (L. The two wires are coloured yellow/black (Hand yellow/brown Land are twisted together to minimise electromagnetic interference (noise) produced by the CAN messages. In the event of a CAN bus failure the following symptoms maybe observed: l Shift from high to low or low to high inoperative l Instrument pack low range warning lamp inoperative l Instrument pack transfer box messages in message centre inoperative.