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U code network Medium severity

U0016 Medium Speed CAN Communication Bus (-) Low

The OBD2 code U0016 indicates a problem with the medium-speed CAN communication bus, specifically that the signal is low, which may suggest a fault in the communication between modules or a wiring issue

Definition

The OBD2 code U0016 indicates a problem with the medium-speed CAN communication bus, specifically that the signal is low, which may suggest a fault in the communication between modules or a wiring issue

Common causes

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

Common misdiagnoses

  • Faulty Engine Control Module (ECM)
  • Defective Body Control Module (BCM)
  • Bad wiring or connectors in the CAN bus
  • Faulty sensors connected to the CAN bus
  • Power supply issues
  • Grounding problems
  • Faulty transmission control module (TCM)
  • Incorrectly configured or programmed 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

  2. 2. Inspect Wiring and Connectors

    Visually inspect the wiring and connectors associated with the Medium Speed 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), Transmission Control Module (TCM), and any other modules that communicate over the Medium Speed CAN

  4. 4. Test the CAN Bus Voltage

    Use a multimeter to measure the voltage on the CAN bus wires. The typical voltage levels should be around 2.5V to 2.8V when the bus is idle

  5. 5. If the voltage is significantly lower, it may indicate a short to ground or a fault in the wiring

  6. 6. Check for Short Circuits

    Inspect the wiring for any short circuits to ground or to other wires. This can cause the bus to read low

  7. 7. Disconnect the battery and perform a continuity test on the CAN bus wires to check for shorts

  8. 8. Test the Modules

    If possible, test the modules that are connected to the Medium Speed CAN bus. A faulty module can cause communication issues

  9. 9. You may need to use a scan tool that can communicate with individual modules to check for faults

  10. 10. Check Termination Resistors

    Ensure that the termination resistors at both ends of the CAN bus are present and functioning correctly. A missing or faulty resistor can lead to communication issues

  11. 11. Inspect Ground Connections

    Check the ground connections for the modules on the Medium Speed CAN bus. Poor ground connections can lead to communication problems

  12. 12. Look for Interference

    Check for any aftermarket devices or modifications that may be interfering with the CAN bus communication

  13. 13. Perform a Network Test

    If you have access to a professional-grade scan tool, perform a CAN bus network test to check for communication between modules

  14. 14. Clear Codes and Test Drive

    After performing the above checks and repairs, clear the trouble codes and take the vehicle for a test drive to see if the code returns.1

  15. 15. Seek Professional Help

    If you are unable to resolve the issue, consider seeking help from a qualified automotive technician who has experience with CAN bus systems. By following these steps, you should be able to identify and resolve the issue related to the U0016 code