NI-CAN 2.x includes a small utility explain.exe, which is typically installed at C:\Program Files\National Instruments\NI-CAN\Utilities. Running this utility from the command line with the error code as a parameter will return a description of the error.
When using LabVIEW, a description of the error can be obtained by selecting Explain Error from the Help Menu. If using LabVIEW 8 or later, it is necessary to have a VI open for this menu option to be visible.
Attached, you will also find the latest error codes for NI-CAN 2.6 in portable document format (PDF) for English (EN), French (FR), German (DE) and Japanese (JP).