In Self Test Mode 2 the node also acknowledges its own data, and a mailbox can be set up to receive a message sent by the same node. The difference compared to Self Test Mode 1 is that there doesn’t have to be a CAN bus connected to the node! Again this can be convenient when testing as this mode allows the CAN controller to run without CAN errors if it is alone on the bus, it acknowledges transmitted frames and can receive messages it has transmitted if desired.