Hi, Akhilesh,
Regarding your question, as you know that the CAN bus is a bus architecture, each CAN node can transmit it's packet to CAN bus, so the arbitration is required, the lower number CAN ID has the higher priority. For arbitration, when the CAN node transmits ID via CAN_TX pin, the CAN_RX of the same CAN module has to receive the ID at the same time so that it can detect if the other CAN node is transmitting. So it does not make sense if you do not connect CAN transceiver and just test the CAN_TX, after you connect CAN transceiver, the CAN_RX can receive the packet the CAN node transmits and the arbitration can be done.
I attach the CAN transceiver schematics, hope it can help you
BR
XiangJun Rong
