🚛 J1939 Sniffer Pro — Python CAN Bus Analyzer with Auto PGN Decoding

Stop staring at raw hex dumps. A professional CAN Bus / J1939 sniffer that decodes 29-bit PGN IDs into engineering units — RPM, °C, km/h — in real time. Built with Python and Tkinter, runs on Windows, macOS, and Linux.

J1939 Sniffer Pro screenshot

J1939 Sniffer Pro

A Python CAN bus and J1939 traffic decoder with 50+ pre-configured PGNs, DM1 fault code parsing, and a built-in traffic simulator — replace $3,000 commercial CAN analyzers with a $59 Python tool.

This is a commercial tool, sold on Gumroad. Source code is included in your purchase.

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What it does

• Real-time J1939 PGN decoding with 50+ pre-configured Parameter Group Numbers
• DM1 fault code parser — see active diagnostic codes from your ECU as text, not raw hex
• Built-in traffic simulator — generate realistic J1939 frames without needing a real truck or genset
• CAN bus support via python-can — works with PCAN, Vector, Kvaser, SocketCAN, virtual CAN
• Live message decoder — SPNs broken out with units (RPM, °C, kPa, %, etc.)
• CSV logging — every decoded message timestamped for offline analysis
• Single-file Python with python-can backend

Why this exists

Commercial J1939 analyzers like Vector CANalyzer cost $3,000-8,000 per seat. Most engineers debugging fleet vehicles, gensets, or off-highway equipment don't need a full suite — they need to decode 10-20 common PGNs and read DM1 fault codes during commissioning.

This tool covers 80% of those workflows for less than 2% of the price.

Pre-configured PGNs include

• EEC1 (Electronic Engine Controller 1) — speed, torque, mode
• EEC2 — accelerator pedal position, load
• DM1 / DM2 — active and previously active diagnostic codes
• VEP1 (Vehicle Electrical Power) — battery voltage, alternator current
• EFC (Engine Fluid Level/Pressure)
• CCVS (Cruise Control / Vehicle Speed)
• AT1IG1 (Aftertreatment 1 Intake Gas)
• TCO1 (Tachograph)
• HOURS — engine total hours, trip distance
• ...and 40+ more

Use cases

Scenario	Why this tool fits
Fleet maintenance debugging	Read DM1 codes without OEM scan tools
Genset commissioning	Verify EEC1/EEC2 messages from new engines
Off-highway equipment	Cummins, Caterpillar, John Deere J1939 streams
ADAS/AV development	Inject simulated CAN traffic for testing
Education / training	Visualize J1939 protocol without real hardware

Get it

→ J1939 Sniffer Pro on Gumroad — $59

Or grab the Industrial Toolkit Bundle ($129) — J1939 + Modbus + MQTT + EtherNet/IP together.

What's in the purchase

• j1939_sniffer.py — Single-file Python application
• pgn_definitions.json — 50+ PGN definitions (extend it yourself)
• requirements.txt — Pinned dependencies
• README.md — Setup guide for PCAN / SocketCAN / Vector
• Commercial use license per Gumroad EULA

License

Commercial use license per Gumroad EULA. You may use this software at the company that purchased it for any commercial purpose. Redistribution, resale, or open-sourcing the code is not permitted.

Support

• Reply to your Gumroad purchase email
• Bug reports / new PGN requests via GitHub Issues

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I write about industrial Python and protocol internals at dev.to/philyeh, and post Chinese versions on iThelp.

— Phil Yeh · Senior Automation Engineer · Industrial Python · Developer Tools