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U code network High severity

U2071 Control Module Communication Bus Off

The OBD2 code U2071 indicates a communication issue where a control module is unable to communicate on the vehicle's communication bus, often due to a fault in the module itself or a wiring issue

Definition

The OBD2 code U2071 indicates a communication issue where a control module is unable to communicate on the vehicle's communication bus, often due to a fault in the module itself or a wiring issue

Common causes

  • Faulty control module
  • Damaged wiring or connectors
  • Poor ground connections
  • Communication bus failure
  • Short circuit in the communication lines
  • Corroded connectors
  • Software issues or bugs in the control module
  • Battery voltage issues
  • Intermittent faults in the communication network
  • Faulty or incompatible aftermarket parts

Common misdiagnoses

  • Faulty control module
  • Wiring issues
  • Poor ground connections
  • Corrupted software/firmware
  • Battery or power supply problems
  • Faulty connectors or terminals
  • Other communication bus errors
  • Sensor malfunctions

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

  2. 2. Inspect Wiring and Connectors

    Visually inspect the wiring and connectors related to the control modules involved. Look for signs of damage, corrosion, or loose connections

  3. 3. Pay special attention to the CAN bus wiring, which typically consists of a twisted pair of wires

  4. 4. Check for Short Circuits or Open Circuits

    Use a multimeter to check for continuity in the CAN bus wiring. Look for any short circuits or open circuits that could be causing communication issues

  5. 5. Test the Control Modules

    If possible, test the control modules involved in the communication. This may involve checking for proper power and ground at the module connectors

  6. 6. If you have access to a known good module, you can swap it in to see if the issue resolves

  7. 7. Inspect the CAN Bus Termination Resistors

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

  8. 8. Check for Interference

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

  9. 9. 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

  10. 10. Update or Reprogram Control Modules

    In some cases, a software update or reprogramming of the control modules may be necessary. Check with the manufacturer for any available updates

  11. 11. Consult Technical Service Bulletins (TSBs)

    Check for any TSBs related to the specific make and model of the vehicle. Manufacturers may have issued guidance on common issues related to U2071

  12. 12. Seek Professional Help

    If the issue persists after performing the above steps, it may be necessary to consult a professional mechanic or technician who has experience with automotive electronics and communication systems. By following these steps, you should be able to identify and resolve the underlying issue causing the U2071 code