BMW CAN Network Problems

What is BMW CAN Network?

CAN, or Controller Area Network integrates BMW control units into one network, which increases communication speeds while reducing the number of wires required for systems to communicate.  

BMW CAN network makes it easy to perform diagnostics using a BMW scanner.

BMW CAN network connect various s including transmission (EGS), Engine Control Module (DME), antilock brake (ABS), traction control/stability control system (DSC), electronic steering, climate control system, lighting control, and many more.

BMW vehicles may have more than one CAN network. Examples of BMW CAN Networks:

• DT  Can (powertrain CAN)
• F-Can (suspension CAN)
• K-Can (body CAN)
• MOST (Media Oriented System Transport)

Symptoms

List of possible symptoms you may notice if the CAN Network or one of its components fails.

• No communication
• No response from a single module
• No communication via the OBD-II port

Common Problems

Possible problems that can trigger fault codes in the CAN Network.

• Damaged or corroded CAN wires
• Poor ground connection
• Failed Control Module
• Water Damage

Troubleshoot BMW CAN Network

Read / clear CAN Network Fault Codes.

If you are experiencing problems, a good starting point is to read fault codes from the CAN Network. If any code is showing PRESENT status, the problem needs to be fixed before the code can be cleared.

What you will need

A diagnostic scanner that is capable of reading, clearing, and performing bi-directional tests on BMW vehicles. You must verify that the scanner that you use supports your BMW model and year. Full system scanners that are known to work on BMW vehicles can range in price from $150 to $800 USD.

List of scanners that read and clear BMW CAN Network fault codes.

• Autel MaxiCOM 
• Foxwell for BMW 
• Launch Full System Scanner 

These are only a few examples. Many diagnostic scanners allow you to read and clear BMW CAN Network fault codes. 

Procedure

1. Plugin the OBD-II scanner into the diagnostic port under the dashboard.
2. Turn on the ignition; don't start the engine.
3. Turn on the scanner and select your BMW chassis. Next, Select the Control Units menu.
4. Select Body then CAN Communication Analysis.
5. Once you enter the CAN Network, you will be able to do the following.
   • Read Codes from CAN Network

CAN Network Fault Codes

There are hundreds of fault codes that can be related to the BMW CAN Network. Below are a few examples of codes stored in BMW CAN Network.

• CDA9 - DME Message A/C Request
• E5C4 - CID K CAN wire fault
• E71E - IHKA Message Torque
• FFFF - CAN SYS Communication Fault

These fault codes will show during network analysis but will be stored in the corresponding control unit as well.

Additional Resources

1. CAN Bus System and Technology - BMW Motorrad UK
2. How to Diagnose a CAN Network - AA1Car.com
3. Investigations on a BMW X5 Can Bus system - techtalk.ie