Why is my CAN bus not working properly?

09 May 2025

This article addresses communication issues on the CAN bus when using Ixxat CAN-IB PCIe boards and USB-to-CAN interfaces. It guides users through essential checks such as wiring, termination, baud rate settings, and signal quality to identify and resolve common CAN bus problems.

 

APPLICABLE PRODUCTS

CAN-IB100/PCIe, CAN-IB200/PCIe, CAN-IB300/PCI, CAN-IB400/PCI, CAN-IB520/PCIe mini, CAN-IB600/PCIe, USB-to-CAN V2, USB-to-CAN FD, CAN@net NT


QUESTION

Why is my CAN bus not working properly?

 

ANSWER

Please check the following things:

  1. Are all CAN nodes connected correctly with each other?
    a) Are the CAN cable and CAN connectors alright?
    b) Is a standard CAN cable used?
    c) Are CAN_H, CAN_L and CAN_GND of the CAN nodes connected with each other?
    d) Is the CAN cable shielded?
    e) Is the Shield grounded at one side?

  2. Is the CAN bus terminated with two CAN termination resistors?

  3. Is the maximum CAN bus length not exceeded?

  4. Are at least two CAN nodes connected to the CAN bus?

    Please note:
    a) For CAN communication at least two CAN nodes are required, because of the CAN acknowledgement.
    b) CAN nodes in „Listen Only“ mode do not send the acknowledgement.

  5. Is the same CAN baud rate set for all CAN nodes?

  6. Is the same CAN mode set for all CAN nodes?
    (standard (11bit ID) or extended (29bit ID)?)

  7. Do all CAN nodes work according to the same CAN standard?
    (ISO 11898 [ISO99-2] (CAN-High-Speed) or ISO 11519 [ISO99-3] CAN-Low-Speed (Fault-Tolerant)).

  8. Are there electrical disturbances on the CAN bus?

  9. Are there CAN Error Frames on the CAN bus?

  10. If you are not able to solve problem, please send to us a CAN topology scheme with the following data

    a) Wire length
    b) CAN baudrate
    c) Location of both CAN termination resistors
    d) Number and type of connected CAN nodes

  11. You can check the quality of the CAN signal using a CANcheck, PCAN-Diag or an oscilloscope?

  12. Please send us screenshots of the CAN signal oscilloscope.