The BMW Network: Marriage of Convenience

February 8, 2018 | Reply More

Feedback we received from our recent survey showed an interest in seeing articles that are based on case studies – actual vehicles with a specific drivability problem that arrive at a shop’s doorstep. So this issue includes not one, but two case studies as experienced by our “tag-team” tech gurus, Augie Ferron and Eric Dibner. Read on and then let us know what you think.

One part of this article and investigation began as “is this how it really works?” The second part was an attempt to keep it simple. The vehicle being tested and interrogated is a 2007 BMW X3 3.0i. The curiosity in the beginning was “What can I see at the data link we are all so familiar with?”

My interest and initial curiosity was to see how the scan tool functions at the DLC. If the homework wasn’t completed, some mistakes and incorrect assumptions can be created when there is a lack of understanding of this BMW network and its “marriage by convenience.” The best place to start is with a detailed schematic and grasping the interconnectivity within this network and with this specific model. In this article (Part 1) we will view the inter-relationship between the scan tool and the network. As for Part 2, using a CAN and or K analyzer will offer a deeper insight.

Keep it simple – or at least try

This BMW had no real issues to speak of, no problems so we decided to look at this vehicle with the simplest and most portable tools possible. Everything was accomplished without creating any faults or damage.

  • Tools used – Keeping it simple and having choices
  • Tested with BMW Rheingold with K + DCAN Cable (Laptop)
  • Tested with Launch EasyDiag (Android Tablet with BMW Application)
  • AR Oscilloscope (2 channel Bluetooth
    with Android Tablet or Laptop)
  • OTC DLC breakout box
  • 90 amp floating power supply
  • A current and specific Data Lines schematic

One word of caution: Any and all KOEO diagnostics MUST have a clean low A/C ripple power supply attached to the electrical system to maintain the required voltage (current) supply, keeping the vehicle alive and stable.

Connectivity and how this was done

K+ DCAN

Rather than “jump” pins 7 and 8 with banana plugs on the break-out box, a switch is preferred to switch diagnosis pins from the new to older models that require pin 8. Closing the switch now makes pins 7 and 8 parallel.

I will assume many of us will use a 4 to 8 channel oscilloscope to view the “K,” “CAN,” or “LIN” BUS signals as they pass throughout the network. The choice was more of an experiment to use a miniature 2 channel battery-operated and Bluetooth-connected oscilloscope module. The requirements were to be: uncomplicated, quick, and effective, with a simplified setup. Another requirement was that the oscilloscope must work with either an Android or a laptop connection. Step 1 was to gather an entire scan.

The EasyDiag was the first scan tool used because of portability, and

 

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Category: Electrical, the bimmer pub

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