Modbus Poll Bytes Missing Error Fixed Jun 2026

This error occurs when the Modbus Poll master expects a specific number of bytes based on the requested function code (e.g., Read Holding Registers) but receives a truncated or incomplete message from the slave device. Response Timeout (Too Short) :

To see exactly what is happening, navigate to within Modbus Poll. This opens a raw hex viewer showing exactly what is being transmitted ( Tx ) and received ( Rx ). Healthy Read (Function 03, 2 Registers): Tx: 01 03 00 00 00 02 C4 OB modbus poll bytes missing error fixed

The "Modbus poll bytes missing error" occurs when a Modbus master device sends a request to a slave device, but the response from the slave device is incomplete or corrupted. Specifically, the master device expects a certain number of bytes in the response, but some of them are missing or not received. This error can cause the master device to lose data, misinterpret data, or even crash. This error occurs when the Modbus Poll master

If you get a "Bytes missing" error, it means you received the first few bytes (e.g., the Slave ID, Function Code, and Byte Count), but the communication dropped out before receiving 00 00 00 0A and the CRC. Healthy Read (Function 03, 2 Registers): Tx: 01

If you've worked through all the steps, use these final checks:

What (e.g., PLC, power meter, sensor) are you trying to read? Share public link

In Modbus TCP or Serial (RTU/ASCII) communication, every message follows a strict structure. When Modbus Poll asks for, say, 10 holding registers, it expects a precise number of bytes back based on the Modbus protocol specifications (e.g., [10 registers × 2 bytes/register = 20 bytes of data + headers]).