WOMS
U code network High severity

U1901 CAN Communication Bus Fault

The OBD2 code U1901 indicates a fault in the CAN (Controller Area Network) communication bus, suggesting a problem with data transmission between modules in the vehicle's network

Definition

The OBD2 code U1901 indicates a fault in the CAN (Controller Area Network) communication bus, suggesting a problem with data transmission between modules in the vehicle's network

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 electrical components
  • Faulty or incompatible aftermarket accessories
  • Software or firmware issues in the control modules
  • Low battery voltage or poor ground connections

Common misdiagnoses

  • Faulty ABS module
  • Defective engine control module (ECM)
  • Malfunctioning body control module (BCM)
  • Wiring issues or shorts in the CAN bus
  • Faulty sensors connected to the CAN bus
  • Bad ground connections
  • Defective transmission control module (TCM)
  • Issues with the instrument cluster
  • Corroded connectors or terminals
  • Battery or power supply problems

Troubleshooting steps

  1. 1. Check for Other Codes

    Use an OBD-II scanner to check for any additional trouble codes. Other codes may provide more context or indicate which module is having issues

  2. 2. Inspect the Wiring and Connectors

    Visual Inspection: Check the wiring harnesses and connectors related to the CAN bus for any signs of damage, corrosion, or loose connections

  3. 3. Repair or Replace

    Repair any damaged wires or connectors as necessary

  4. 4. Check the CAN Bus Termination Resistors

    Ensure that the CAN bus has the correct termination resistors (typically 120 ohms) at both ends of the bus. A missing or faulty resistor can cause communication issues

  5. 5. Test the Modules

    Module Functionality: Check the functionality of the modules on the CAN bus. If one module is malfunctioning, it can disrupt communication

  6. 6. Communication Test

    Use a scan tool to see if you can communicate with all modules on the bus. If one module is unresponsive, it may need to be repaired or replaced

  7. 7. Check for Short Circuits

    Use a multimeter to check for short circuits in the CAN bus wiring. A short can cause communication failures

  8. 8. Inspect the Battery and Ground Connections

    Ensure that the vehicle's battery is in good condition and that all ground connections are clean and secure. Poor power or ground can lead to communication issues

  9. 9. Look for Interference

    Check for any aftermarket devices or modifications that may interfere with the CAN bus communication. This includes alarms, stereo systems, or other electronic devices

  10. 10. Perform a Network Test

    If available, use a specialized CAN bus diagnostic tool to perform a network test. This can help identify issues with the bus itself

  11. 11. Clear Codes and Test Drive

    After performing repairs, clear the trouble codes and take the vehicle for a test drive to see if the code returns

  12. 12. Seek Professional Help

    If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or technician who specializes in automotive electronics. By following these steps, you should be able to identify and resolve the underlying issue causing the U1901 code