The TCAN1043A-Q1 device can detect the following six fault conditions and set the nFAULT pin low as an interrupt so that the controller can be notified and act if a CAN bus fault exists. These failures are detected while transmitting a dominant signal on the CAN bus. If one of these fault conditions persists for four consecutive dominant-to-recessive bit transitions, the nFAULT indicates a CAN bus failure flag in Normal mode by driving the nFAULT pin low. The CAN bus driver remains active. Table 8-2 shows what fault conditions can be detected by the TCAN1043A-Q1.

Bus fault detection is a system level situation. If the fault is occurring at the ECU the general communication of the bus may be compromised. Until a diagnostic determination can be made the transceiver remains in CAN active mode during a CAN bus fault enabling the ECU to transmit data to the CAN bus and receive data from the CAN bus. For complete coverage of a node, a system level diagnostic step should be performed for each node and the information should be communicated back to a central point.

While in normal mode, if no CAN bus fault is detected for four consecutive dominant-to-recessive transitions on the TXD pin then the CBF flag is cleared and nFAULT is driven high. The bus fault failure circuitry is able to detect bus faults for a range of differential resistance loads (R_CBF) and for any time greater than t_CBF.