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  • JCOM1939 Monitor - Main Screen
  • JCOM1939 Monitor - ECU Setup
  • JCOM1939 Monitor - Filter Messages
  • JCOM1939 Monitor - Scan Network
  • JCOM1939 Monitor - Simulate analog signals
  • JCOM1939 Monitor - Simulate digital signals
  • JCOM1939 Monitor - Recording data traffic to PC

JCOM1939 Monitor Pro - SAE J1939 Data Monitor, Recorder, Simulator

Free Download

Product Description

This is a free download!

The JCOM1939 Monitor Software is the perfect tool to monitor, record, analyze, and simulate SAE J1939 data traffic. The system works in combination with our SAE J1939 gateways.

This comprehensive and easy-to-use, easy-to-understand Windows software displays not only SAE J1939 data traffic; it also allows to scan the network, simulate an ECU (incl. full node address negotiation features), and respond to data request messages.

The communication protocol between the gateway and the host system (PC, Embedded System, Android System, etc.) is well documented, and we provide C/C# source code to read and write CAN data frames.


  • FREE download
  • ECU Simulation Setup (Preferred Node Address, Negotiable Address Range, NAME, and more)
  • Filter J1939 PGNs for Display
  • Design J1939 PGNs for Transmission (Data and Request Messages)
  • Design J1939 PGNs for Request Responses
  • Simulate Digital and Analog Signals
  • Scan a J1939 Network (Number of Nodes, Node IDs, NAMEs)
  • Record SAE J1939 Data Traffic
  • Simulate SAE J1939 Data Traffic
  • Check Gateway Status (Error Messages, Software/Hardware Version)
  • Set Gateway Parameters (Heartbeat Frequency, Message Acknowledgment)
  • Free Updates

SAE J1939 Gateways

The JCOM1939 Monitor software works directly with the following SAE J1939 gateways:


Development Resources

Program Versions And Update

Start your version of the jCOM1939 Monitor and check the version number in the window’s caption (top bar).

JCOM1939 Monitor - Check Version Number

If your version is older than the one as shown below, we strongly recommend to download and install the newest version.

The jCOM1939 Monitor for Windows is free software; you can redistribute it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License or (at your option) any later version. The program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. With downloading these programs, you confirm that you have read and agree with these terms and conditions.

The newest version is
V 3.40.01


After downloading the installation program, run the .exe program and follow the instructions on the screen to install the program. This is a standard installation program for Windows; there are no special actions or settings necessary.

Version History

  • V 1.02.00

    • First release
  • V 2.00.00

    • Periodic messages are managed in gateway instead of Windows software
    • Added application file functionality
  • V 3.00.00

    • Professional version release
    • Replaced Windows control modules to eliminate screen flickering
    • Optimized screen update timing
  • V 3.01.00

    • Added support for multiple instances of the program to allow connection of several gateways per PC
    • Transport Protocol (TP) messages (data frames longer than 8 bytes) cannot be assigned a frequency anymore since that is not part of the J1939 standard
    • Misc. memory optimizations
    • Misc. speed optimizations
  • V 3.01.01

    • Debugging: Checksum and byte stuffing errors plus HW/SW version were only displayed after first heartbeat message
  • V 3.10.00

    • Added SAE J1939 Data Recording (new Recorder tab).
  • V 3.10.01

    • ACK messages are disabled at program start to reduce data traffic between the gateway and the PC.
    • Previous versions allowed to enter a destination address (DA) for a Broadcast PGN, which was ignored but may confuse users. The program now displays a message and sets the DA to the global address 255.
  • V 3.10.02

    • Due to the previous software update, the PGN description on the data screen was suppressed.
  • V 3.11.00

    • The PGN data display has been extended to indicate whether the SAE J1939 data frame was received or transmitted.
    • The software now adds the selected CAN baud rate (250/500k) to the application file.
    • Resolved some application file saving issues.
    • Added C-tech icon (so far we’ve used the Microsoft Visual Studio default).
  • V 3.20.00

    • Editing of Tx Data is now allowed without claiming ECU address first
    • Added tab for editing data bytes (simulation of analog parameters)
    • Added tab for editing data bits (simulation of digital parameters)
  • V 3.20.01

    • Bit Data Editing: The bit sequence text (“8 7 6 5 4 3 2 1”) above the bit checkboxes was reversed.
  • V 3.30.00

    • A message request required the data entry field to be filled by the user, otherwise there would be an error message. However, the data entry was not necessary, since it’s being created automatically by the software.
    • Added support for new devices with RTC (real-time clock) and SD card.
    • Data view table includes time stamps for devices with RTC.
    • Heartbeat message was extended to include functionality information (RTC, SD Card).
  • V 3.30.01

    • We took care of a bug in the data recording section. The data fields for source address (SA) and destination address (DA) were switched.
  • V 3.31.00

    • There is now a new tab “Settings” that allows to individually switch PGN, Source Address (SA), Destination Address (DA), and Data between decimal and hex.
    • The Recording file now includes the PGN description.
  • V 3.40.00

    • Modified the J1939 data display to accomplish higher display speeds.
    • Addressed a bug that prevented saving filter PGNs to the application file in certain cases.
  • V 3.40.01

    • Code optimization for new ESP32-based gateways.

A Comprehensible Guide to J1939

A Comprehensible Guide to SAE J1939

SAE J1939 has become the accepted industry standard and the vehicle network technology of choice for off-highway machines in applications such as construction, material handling, and forestry machines. J1939 is a higher-layer protocol based on Controller Area Network (CAN Bus).

It provides serial data communications between microprocessor systems (also called Electronic Control Units - ECU) in any kind of heavy duty vehicles. The messages exchanged between these units can be data such as vehicle road speed, torque control message from the transmission to the engine, oil temperature, and many more.

The information in this book is based on two documents of the SAE J1939 Standards Collection: J1939/21 - Data Link Layer J1939/81 - Network Management A Comprehensible Guide to J1939 is the first work on J1939 besides the SAE J1939 standards collection.

It provides profound information on the J1939 message format and network management combined with a high level of readability.


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