That standard covers DM1 (active DTCs), DM2 (previously active DTCs), DM3 (clear DTCs), DM4 (freeze frame), etc. It's widely used in commercial vehicle diagnostics.
Among the most sought-after documents in this series is , titled “Diagnostics – Application Layer – Diagnostic Messages.” This document is critical for anyone building diagnostic tools, troubleshooting heavy-duty vehicle faults, or designing compliance-ready ECUs.
: Provides specialized feedback for emissions compliance reporting. Technical Implementations and Challenges sae j193973 pdf exclusive
If you're interested in obtaining the SAE J1939.73 PDF, please visit the official SAE website or contact their customer support team for more information.
Go to the SPN index. Step 2 (Look up SPN 91): You find "Accelerator Pedal Position 1." Step 3 (Look up FMI 3): You go to the FMI table. FMI 3 = "Voltage Above Normal or Shorted High." Step 4 (The Diagnosis): You don't just guess. The PDF tells you that combination means the ECU sees 5+ volts on the pedal sensor circuit when it should see 0.5-4.5 volts. You now know to look for a short to power. That standard covers DM1 (active DTCs), DM2 (previously
The standard specifies how Electronic Control Units (ECUs) report their status during both vehicle operation and repair . Key functions include:
I can provide or troubleshooting steps for common DMs if you'd like. Step 2 (Look up SPN 91): You find
This is a one-time purchase. You pay a fee, and you receive a static PDF file. You "own" that version forever, but you do not receive updates. If SAE releases a 2026 version, you must buy it again. This is best for hobbyists or students who need a specific historical version.
Used to erase inactive codes from the ECU memory.
A Diagnostic Trouble Code in J1939-73 is transmitted as 4 bytes: