WOMS
U code network Medium severity

U1906 U1906: "CAN Communication Malfunction

The OBD2 code U1906 indicates a malfunction in the Controller Area Network (CAN) communication system, which affects the ability of various vehicle modules to communicate with each other

Definition

The OBD2 code U1906 indicates a malfunction in the Controller Area Network (CAN) communication system, which affects the ability of various vehicle modules to communicate with each other

Common causes

  • Faulty CAN bus wiring or connectors
  • Defective CAN bus module
  • Short circuit in the CAN bus
  • Open circuit in the CAN bus
  • Interference from other electronic devices
  • Faulty or incompatible aftermarket accessories
  • Poor ground connections
  • Corroded or damaged terminals
  • Software or firmware issues in the control modules
  • Low battery voltage or power supply issues

Common misdiagnoses

  • Faulty CAN bus wiring
  • Defective control modules
  • Poor ground connections
  • Corroded connectors
  • Intermittent electrical issues
  • Software glitches in modules
  • Faulty sensors
  • Battery or charging system problems

Troubleshooting steps

  1. 1. Check for Additional Codes

    Use an OBD-II scanner to check for any other trouble codes that may be present. Other codes can provide context and help identify the root cause of the communication issue

  2. 2. Inspect the Wiring and Connectors

    Visually inspect the wiring and connectors related to the CAN bus. Look for signs of damage, corrosion, or loose connections

  3. 3. Pay special attention to the connectors at the Engine Control Module (ECM), Body Control Module (BCM), and any other modules that communicate over the CAN bus

  4. 4. Test the CAN Bus Voltage

    Use a multimeter to measure the voltage on the CAN High (CAN H) and CAN Low (CAN L) wires. The typical voltage levels should be around 2.5V when the bus is idle

  5. 5. If the voltage levels are significantly off, there may be a short circuit or an open circuit in the wiring

  6. 6. Check for Short Circuits or Open Circuits

    Use a multimeter to check for continuity in the CAN bus wiring. Look for any shorts to ground or power, as well as open circuits that could disrupt communication

  7. 7. Inspect Modules for Faults

    Check the individual modules on the CAN bus for faults. A malfunctioning module can disrupt communication for the entire network

  8. 8. If possible, perform a module reset or reprogramming to see if that resolves the issue

  9. 9. Look for Interference

    Ensure that there are no aftermarket devices or modifications that could be interfering with the CAN bus communication. This includes alarm systems, stereo systems, or other electronic devices

  10. 10. Check for Software Updates

    Verify if there are any software updates available for the vehicle’s modules. Sometimes, manufacturers release updates to fix known communication issues

  11. 11. Perform a Network Test

    If you have access to a professional-grade scan tool, perform a network test to check the status of the CAN bus and the modules connected to it

  12. 12. Clear Codes and Test Drive

    After performing the above checks and repairs, clear the trouble codes using the OBD-II scanner and take the vehicle for a test drive to see if the code returns

  13. 13. Consult a Professional

    If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or technician who specializes in automotive electronics and CAN bus systems. By following these troubleshooting steps, you can systematically identify and resolve the underlying issues causing the U1906 code