Sae J1939-73 Pdf (2026)
(Exact PGN numbers and field formats are in the SAE J1939-73 specification—consult the standard PDF for full byte-level definitions.)
A DM is a Parameter Group Number (PGN) that carries one or more DTCs and related status information. The J1939-73 standard defines numerous DMs, but three are the most fundamental:
Beyond just reporting errors, the protocol allows modules to share information so they can self-compensate for minor issues before a full breakdown occurs. The PDF: A Living Technical Bible
: Enables service tools to trigger specific test modes to verify subsystem operations. Essential Diagnostic Messages (DM) Sae J1939-73 Pdf
The role of SAE J1939-73 is set to expand significantly as the heavy-duty industry embraces electrification and connectivity.
While the broader J1939 standard dictates how electronic control units (ECUs) talk to each other over a Controller Area Network (CAN bus), specifically governs Application Layer – Diagnostics .
Because this is a copyrighted technical standard, it is typically not available for free as a full PDF. You can purchase the official document or access its summary through the SAE International Standards Store (Exact PGN numbers and field formats are in
Yes, but extended. The latest revisions add DM33 for HV battery isolation monitoring and DM34 for traction motor diagnostics. Always download the most recent PDF for EV/HEV work.
| Field | Name | Description | | :--- | :--- | :--- | | | Suspect Parameter Number | A 19-bit number identifying which specific component or system has failed (e.g., the SPN for "Engine Oil Pressure" is 100). | | FMI | Failure Mode Identifier | A 5-bit number describing the type of failure (e.g., FMI 1 means "Data Valid But Below Normal Operational Range - Most Severe Level"). | | OC | Occurrence Count | A 7-bit count of how many times the DTC has transitioned from active to previously active, helping track intermittent faults. | | CM | Conversion Method | A 1-bit field indicating how the SPN should be interpreted. |
specifically covers the Application Layer – Diagnostics . Officially titled "Diagnostic Application Layer," this document outlines: Essential Diagnostic Messages (DM) The role of SAE
: Heavy-Duty On-Board Diagnostics regulations in regions like North America (CARB/EPA) and Europe (Euro VI) mandate the use of specific J1939-73 messages (such as DM12 and DM19) to ensure emissions enforcement agencies can read vehicle emissions compliance data.
Having the PDF is only half the battle. To use the standard effectively, pair it with one of these diagnostic tools:
When a technician plugs a service tool into the diagnostic connector, J1939-73 dictates the "handshake" that allows the tool to read the vehicle’s memory, clear old fault codes, or even perform security functions.