When working with the Controller Area Network (CAN) bus—whether in automotive, industrial automation, robotics, or embedded systems—you’ll quickly notice that most CAN connectors include a ground pin. At first, this may seem unnecessary because CAN uses differential signaling. If the data is transmitted as a difference between CAN-H and CAN-L,…
Posts published in “JCOM1939 Practical Guide”
The JCOM1939 Practical Guide is a growing collection of hands-on tutorials, technical articles, and real-world examples designed to help engineers, developers, technicians, and enthusiasts get the most from the JCOM1939 Monitor Software and JCOM1939 gateways.
If you’re learning SAE J1939, you’ll quickly run into two acronyms that show up everywhere—in diagnostic messages, simulation tools, engine logs, and OEM documentation: SPN (Suspect Parameter Number) FMI (Failure Mode Identifier) Together, SPNs and FMIs explain what went wrong and how it went wrong.They form the core of every…
If you’re new to SAE J1939, one of the first things you’ll encounter is how heavy-duty vehicles report problems. They do this using standardized diagnostic messages, and the two most important are: DM1 — Active Diagnostic Trouble Codes DM2 — Previously Active Diagnostic Trouble Codes Understanding these two messages will…
SAE J1939 is a family of Controller Area Network (CAN) based standards used in heavy‑duty vehicles for powertrain control and diagnostics. Historically, the standard specified a 250 kbit/s data rate, which has been adequate for networks containing a handful of Electronic Control Units (ECUs). Modern trucks now incorporate dozens of ECUs,…
This article is part of our comprehensive SAE J1939 online documentation. The primary document describing the J1939 message format is SAE J1939/21 – Data Link Layer. This specification defines the use of the CAN data frame (29-bit identifier, Parameter Group Numbers – PGN, etc.) as well as the transport protocol…
This article is part of our comprehensive SAE J1939 online documentation. The SAE J1939 Standards Collection serves as the comprehensive framework for communication and control within truck, bus, and off-road vehicle networks. It defines how electronic control units (ECUs) exchange data over the Controller Area Network (CAN), detailing message structures,…
Controller Area Network (CAN bus) is a widely used communication network in automotive and industrial systems. It provides a robust, real-time communication method for multiple microcontroller-based devices (nodes) to exchange data over a simple two-wire bus. In industrial environments, proper network design is critical to ensure reliable performance under noise,…
One of the most common questions we receive from users involves the J1939 Address Claim process when connecting our J1939 gateways to another J1939 node. Many expect the address claim to succeed immediately, but under certain conditions it may fail. Understanding why this happens will save you both time and…
This guide walks you through the quick and straightforward process of setting up the JCOM.J1939.USB gateway board. You’ll learn how to establish the USB connection, hook up the SAE J1939/CAN bus interface, and confirm that everything is functioning properly, including LED indicators. This post focuses purely on text explanation—with bullet…
When working with Controller Area Network (CAN) and higher-layer protocols like SAE J1939, one feature that often confuses users is the Silent Mode (also known as Listen-Only Mode). While simple in concept, misunderstanding how it affects communication can lead to frustrating troubleshooting scenarios, especially when setting up or testing J1939…
