![SWTB_logo_rgb_color_mode-wPadding-2000x961.png]](https://help.softwaretoolbox.com/hs-fs/hubfs/SWTB_General/Images/Press_Kit/SWTB_logo_rgb_color_mode-wPadding-2000x961.png?height=50&name=SWTB_logo_rgb_color_mode-wPadding-2000x961.png){kind=logo}
Modbus Vendor-Specific (Non-Standard) Exception Codes
The exception code I am receiving is not listed in the standard Modbus Exception codes in the product help files. How do I know what the problem is?
While the Modbus protocol defines a set of standard exception codes, some device vendors implement non-standard (meaning vendor-specific) codes to report conditions unique to their hardware or firmware. These codes are not part of the official Modbus spec and their meaning can vary between manufacturers. Additionally, these non-standard codes are commonly used and seen coming from gateway devices and not necessarily the target device.
If you encounter one of these codes, you will need to consult the target device/gateway vendor documentation or vendor technical support for exact definitions and troubleshooting steps.
Below is an example of a vendor-specific code we have seen in the field:
| Code (Dec/Hex) | Vendor / Example Device | Meaning / Notes |
|---|---|---|
| 66 / 0x42 | ICP DAS / TGW-715 | "Gateway target device failed to respond " Indicates the gateway did not receive a response from the target device. (Functions the same as standard code 11) |
Vendor-specific codes are not defined by the Modbus standard, so the same numeric code may mean different things for different devices. Always confirm meaning and resolution steps with the device vendor’s manuals or support resources.
For reference to standard Modbus exception codes, see our Standard Modbus Exception Codes FAQ