WOMS
U code network High severity

U1273 Communication Bus Off

The OBD2 code U1273 indicates a communication issue where the vehicle's communication bus is offline or not functioning properly, often related to a failure in the network that connects various control modules

Definition

The OBD2 code U1273 indicates a communication issue where the vehicle's communication bus is offline or not functioning properly, often related to a failure in the network that connects various control modules

Common causes

  • Faulty wiring or connectors in the communication bus
  • Malfunctioning control modules
  • Short circuits or open circuits in the bus lines
  • Corroded or damaged connectors
  • Power supply issues to the control modules
  • Software or firmware issues in the modules
  • Interference from aftermarket devices or modifications

Common misdiagnoses

  • Faulty ECM (Engine Control Module)
  • Bad wiring or connectors
  • Defective sensors
  • Malfunctioning ABS module
  • Issues with the body control module (BCM)
  • Powertrain control module (PCM) problems
  • Battery or charging system issues
  • Faulty communication lines or networks
  • Incorrectly installed aftermarket accessories
  • Software or firmware issues in control modules

Troubleshooting steps

  1. 1. Check for Additional Codes

    Use an OBD-II scanner to check for any other trouble codes that may be present. This can provide more context about the issue and help identify the faulty module

  2. 2. Inspect Wiring and Connectors

    Visually inspect the wiring and connectors related to the communication bus. Look for signs of damage, corrosion, loose connections, or broken wires. Pay special attention to the CAN (Controller Area Network) bus wiring

  3. 3. Check the Battery and Ground Connections

    Ensure that the vehicle's battery is in good condition and that all ground connections are secure. A weak battery or poor ground can cause communication issues

  4. 4. Test the Communication Bus

    Use a multimeter or an oscilloscope to check the voltage levels and signal integrity on the communication bus. Compare the readings to the manufacturer's specifications

  5. 5. Inspect Modules

    Identify the modules that are connected to the communication bus. Check for any signs of physical damage or water intrusion. If a specific module is suspected to be faulty, it may need to be tested or replaced

  6. 6. Perform a Network Test

    Some advanced scan tools can perform a network test to check the communication between modules. This can help identify which module is not communicating properly

  7. 7. Clear Codes and Test Drive

    After performing inspections 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

  8. 8. Check for Software Updates

    In some cases, a software update for the vehicle's control modules may resolve communication issues. Check with the manufacturer for any available updates

  9. 9. Consult Technical Service Bulletins (TSBs)

    Look for any TSBs related to the U1273 code for your specific vehicle make and model. Manufacturers may have issued guidance on common issues and fixes

  10. 10. Seek Professional Help

    If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or technician who has experience with automotive electronics and communication systems. By following these troubleshooting steps, you can systematically identify and resolve the underlying issue causing the U1273 code