J1939 Explained - A Simple Intro [v2.0 | 2021] 🌟

What is J1939?
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In short, J1939 is a set of standards defined by SAE (Society of Automotive Engineers) that define how electronic control units (ECUs) communicate via the CAN bus in heavy-duty vehicles. It is a higher layer protocol and serves as a standard for e.g. trucks, buses, excavators, tractors - across different manufacturers and brands. Further, J1939 serves as the basis for derived protocols like NMEA 2000 (maritime) and ISOBUS (agriculture). Within J1939, a 250K or 500K bit rate is used and 29-bit extended CAN frame identifiers (CAN 2.0B). CAN signals are called Suspect Parameter Numbers (SPN) and are grouped by their Parameter Group Number (PGN) within CAN frames. Because of the standardized nature of J1939, it enables both manufacturers (OEMs) and after market users to record as well as interpret raw data from heavy duty vehicles using e.g. CAN bus data loggers.
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In this "v2.0" updated video tutorial we explain the J1939 standard:
- 00:00 Introduction
- 00:23 Basics of J1939 (incl. the 7 layer OSI model)
- 01:58 History of J1939
- 02:49 Key properties of J1939
- 03:50 The J1939 PGN and SPN
- 06:12 How to decode J1939 data to physical (example)
- 07:21 How to log J1939 data in practice (incl. the J1939 DBC)
- 09:21 Examples: J1939 data logging use cases
This video is part of our extremely popular series of CAN protocol intros. Below you'll find links for our full playlist, as well as the more detailed articles.
Playlist for all intro videos: • CAN Bus Explained - A ...
If you're interested in learning more about logging CAN bus data, we recommend that you check out our below intros to our CANedge CAN bus data loggers, our CANmod sensor-to-CAN modules and our free software/API tools:
Learn about CAN bus data logging:
• CANedge: CAN Bus Data ...
Learn about the CANedge and CANmod:
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1) CANedge1: www.csselectronics.com/produc...
2) CANedge2: www.csselectronics.com/produc...
3) CANedge3: www.csselectronics.com/produc...
4) CANmod.gps: www.csselectronics.com/produc...
5) CANmod.temp: www.csselectronics.com/produc...
6) CANmod.input: www.csselectronics.com/produc...
See also our intros to practical J1939 logging & software:
1) J1939 data logger: www.csselectronics.com/pages/...
2) J1939 dashboards: www.csselectronics.com/pages/...
3) J1939-to-USB interface: www.csselectronics.com/pages/...
4) asammdf GUI: www.csselectronics.com/pages/...
5) J1939 reverse engineering: www.csselectronics.com/pages/...
6) J1939 DBC: www.csselectronics.com/produc...
For more tutorials, see our overview: www.csselectronics.com/pages/...
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At CSS Electronics we specialize in simple-to-use, pro specs and interoperable CAN bus data loggers - like the CANedge and CLX000 series. The devices let you record raw data from e.g. cars, trucks, industrial machinery and other CAN based applications onto an 8-32 GB SD card. The devices are interoperable, meaning you can process the data in your favorite existing software - or use our 100% free and open source software/API tools.
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[@neerja1384]

Behind music is so good it feels like really learning ,progress and the way it explained wonderful 👍👍👍

[@Dragoneer]

Very well explained and informative video, thank you! I have since learned CAN bus physical/transport layers (including the 4 message frame types) and have been using the CANopen protocol to program a number of PLCs professionally, but have seen this j1939 protocol being used a few times with CAN 2.0B especially within the IC engine ECUs (I’ve only really needed to use 2.0A so far). Hence, this has inspired me to start learning it so I can understand and control how our PLC/ECUs components talk to each other! :D SAE 1939-71 is going to fair out to be a _very_ useful reference I imagine…

[@martinfalch4648]

Thanks for the feedback! Yes, J1939-71 would be a good resource for the purpose of recording J1939 data :-) See also our J1939 DBC that takes the contents of the J1939-71 PDF (PGNs & SPNs) and puts it in the standardized DBC format.

[@alexdent7425]

Very clean, clear and easy to follow great video!

[@ELEISONCARABALLO]

Awesome video, thanks for sharing

[@patrickchiapello4344]

Thank you!Very useful!

[@martinfalch8016]

Thank you!

[@snehakumbhar8349]

Wonderful understanding ...

[@CSSElectronics-CAN-Logger-X000]

Let us know if you have any questions regarding the J1939 protocol!

[@adrianburrows1169]

how do I connect to the 3 pin connector via diagnostics. I have 493033 data link connector from Cummins inline 7. I cannot find any tutorials and or anything relative on using this through diagnostic software.

[@_tranquangtien8854]

Hi, why J1939 is only used in trucks? it seams to me a good protocol that car manufactures can benefit from too right, given they already have their CAN infrastruture

[@bart08]

@@_tranquangtien8854 i know that it is used in fendt tractors too

[@subhrasoiandvlogs]

amazed with explaination.....very helpful video

[@rayenbenmahmoud4002]

Well detailed, thank you i learned a lot from this video

[@martinfalch8016]

Glad to hear Rayen!

[@chandanakumara9697]

Thank

[@apollocolorado]

Helpful information. Starting around 2:50, it appears that the slides are incomplete.

[@davidkallai5564]

Hello, Could you tell me please if I want to reprogram a tractor display to add one more language to it how can I start? I don't have any experience in programming but now I want to learn. Could you tell me some instruction?

[@yudhahamdiarzi5553]

Thank you for the explanation, I am now learning J1939 Can for fleet management. So the best practice to extract data from vehicle is to log it first, decode and decide what data that we need to extract?

[@martinfalch4648]

Our recommendation is at least that you should start by "logging everything" during an initial evaluation period. You can then DBC decode the data and review what CAN IDs you can decode and which of them contain data that is relevant to your use case. All irrelevant CAN IDs can be filtered out via the CANedge configuration. For the remaining relevant CAN IDs, we then suggest to evaluate what frequency you need the data at. For example, Engine Speed is typically broadcast at 500-1000 Hz on the CAN bus, but most use cases need it at only 1-10 Hz. By using our prescalers to handle this on the device you can typically reduce your data size by 95%+ without loosing relevant information.

[@olivioferreira2418]

What it means the code MpJ1939? (In this case i want to know about "Mp" that is included)

[@vahidogbamey4828]

My truck displays a fault code CAN j1939 active fault.

[@sujana9200]

How can mapped to j1939 please explain it