Fleet management has evolved far beyond simply knowing where a vehicle is located. Modern commercial vehicles continuously transmit enormous amounts of operational data through the SAE J1939 network, while GPS receivers provide precise positioning information. Together, these technologies form the foundation of telematics, enabling fleet operators to monitor vehicle performance,…
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.
Designing a CAN Bus device that performs well under ideal conditions is relatively straightforward. The real challenge begins when the network no longer behaves as expected. In the field, connectors loosen, ECUs lose power, messages are delayed, wiring deteriorates, and configuration errors inevitably occur. A robust CAN device must continue…
When engineers troubleshoot a CAN network, they usually focus on the messages flowing across the bus. They check identifiers, decode data bytes, and verify timing. While that is certainly important, there is another source of diagnostic information that is often overlooked—and in many cases, it provides the fastest path to…
In this post, I would like to address what is arguably the most important concept in the SAE J1939 standard: the Parameter Group Number (PGN). PGNs are the heart and soul of J1939. Every application you design, whether it transmits engine speed, requests a VIN, or reports diagnostic information, revolves…
When the first versions of SAE J1939 emerged in the late 1980s and early 1990s, the objective was straightforward: provide a standardized communication protocol for electronic control units (ECUs) in heavy-duty trucks. At the time, vehicle manufacturers were rapidly increasing the number of electronic subsystems, creating a need for a…
If you’ve worked with SAE J1939 long enough, you’ve probably experienced the frustration of connecting two devices to a CAN bus and seeing… absolutely nothing happen. No engine data. No diagnostic messages. No responses to requests. Just silence. The good news is that most J1939 communication problems are caused by…
In previous quick demos, we focused on SAE J1939 parameters that are transmitted periodically, such as engine speed, vehicle speed, fuel level, and engine temperatures. These messages are broadcast automatically at predefined intervals, allowing any node on the network to receive the data without explicitly asking for it. The Vehicle…
Engine speed is one of the most frequently monitored parameters in any SAE J1939 network. Whether you are developing a dashboard, testing an engine ECU, validating telematics software, or learning how J1939 communication works, engine speed is often the first parameter engineers look at. In this post, we will explain…
One question that appears regularly in SAE J1939 discussions is whether multiple Electronic Control Units (ECUs) can transmit the same Parameter Group Number (PGN). At first glance, the answer seems straightforward: if the J1939 standard defines a message, why shouldn’t multiple devices be allowed to transmit it? In reality, the…
One of the most common misconceptions in the heavy-duty vehicle and industrial control markets is the assumption that a device using CAN 2.0B with a 29-bit identifier is automatically SAE J1939 compatible. Unfortunately, that assumption has caused countless integration headaches, wasted engineering hours, and unnecessary investments in development tools and…
