Device (12; 32) for a serial bus system, having a transmission signal analysis module for counting edges of a transmission signal (TxD) that is to be sent to a bus of the bus system in order to exchange a message between subscriber stations (10, 20, 30) of the bus system, a transmission module for sending a message based on the transmission signal (TxD) to the bus, a received signal analysis module for counting edges of a received signal (Rx_In) generated from a signal transmitted on the bus based on the transmission signal (TxD), wherein the bus states (401, 402) of the signal transmitted on the bus for the message in a first communication phase (451; 453, 451) differ from bus states (U_D0, U_D1) of the signal transmitted on the bus in a second communication phase of the message, the signal transmitted on the bus based on the transmission signal (TxD) being able to be overlapped by a signal that has been put onto the bus by another subscriber station (10, 20, 30) of the bus system, and an evaluation module for evaluating the difference that arises from a comparison of the edges counted by the transmission signal analysis module and the edges counted by the received signal analysis module, wherein if the signal propagation time on the bus that the signal (CAN_H, CAN_L) generated from the transmission signal (TxD) has before the received signal (Rx_In) is received at the device (12; 32) is greater than the bit time (t_b2) of the received signal (Rx_In), the evaluation module is configured to signal whether the absolute value of the difference is less than or equal to a predetermined value, or whether the absolute value of the difference is greater than the predetermined value, and wherein the predetermined value is greater than zero. a transmission module for sending a message based on the transmission signal (TxD) to the bus, a received signal analysis module for counting edges of a received signal (Rx_In) generated from a signal transmitted on the bus based on the transmission signal (TxD), wherein the bus states (401, 402) of the signal transmitted on the bus for the message in a first communication phase (451; 453, 451) differ from bus states (U_D0, U_D1) of the signal transmitted on the bus in a second communication phase of the message, the signal transmitted on the bus based on the transmission signal (TxD) being able to be overlapped by a signal that has been put onto the bus by another subscriber station (10, 20, 30) of the bus system, and an evaluation module for evaluating the difference that arises from a comparison of the edges counted by the transmission signal analysis module and the edges counted by the received signal analysis module, wherein if the signal propagation time on the bus that the signal (CAN_H, CAN_L) generated from the transmission signal (TxD) has before the received signal (Rx_In) is received at the device (12; 32) is greater than the bit time (t_b2) of the received signal (Rx_In), the evaluation module is configured to signal whether the absolute value of the difference is less than or equal to a predetermined value, or whether the absolute value of the difference is greater than the predetermined value, and wherein the predetermined value is greater than zero.