A JCOM1939 Engineering Note on Error Handling, Bus Off, and Silent Mode in Two-Node CAN Networks JCOM1939.com | Copperhill Technologies | © 2026 Controller Area Network (CAN) is well known for its robustness. Arbitration prevents message collisions from corrupting data, error detection identifies damaged frames, automatic retransmission provides another opportunity…
Posts tagged as “J1939”
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,…
It has been a while since we released new functionality for the JCOM1939 Monitor software for Windows, but recent customer feedback inspired several improvements that make the software even more valuable during development, troubleshooting, and diagnostics. The latest update introduces two important features: Display of the CAN Bus network condition,…
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…
Modern digital dashboards are amazing. They offer colorful displays, engine diagnostics, fuel consumption data, trip information, and customizable gauges that make a 20-year-old truck feel like a brand-new vehicle. Unfortunately, many truck owners discover a frustrating reality after installation: The dashboard powers up perfectly, but no engine data appears on…
As heavy-duty vehicles become increasingly connected, engineers are looking for ways to integrate vehicle data into fleet management systems, cloud applications, industrial control systems, and enterprise databases. The hardware needed for such integrations is readily available. Products from companies such as Red Lion, Moxa, HMS, Sierra Wireless, and many others…
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…
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…
In the world of heavy-duty vehicles and agricultural machinery, communication standards are essential for interoperability, diagnostics, and control. Two of the most prominent protocols in this space are SAE J1939 and ISOBUS (ISO 11783). While they share a common technical foundation—both being based on the CAN (Controller Area Network) bus—they…
