WOMS
U code network High severity

U0023 Low Speed CAN Communication Bus (+) High

The OBD2 code U0023 indicates a fault in the low-speed CAN communication bus, specifically that the positive signal line is experiencing a high voltage condition, which may disrupt communication between modules

Definition

The OBD2 code U0023 indicates a fault in the low-speed CAN communication bus, specifically that the positive signal line is experiencing a high voltage condition, which may disrupt communication between modules

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
  • 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 CAN bus module
  • Faulty ECU (Electronic Control Unit)
  • Bad ground connections
  • Intermittent electrical connections
  • Faulty sensors connected to the CAN bus
  • Software issues or programming errors
  • Battery or power supply issues

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 additional context for the issue

  2. 2. Inspect Wiring and Connectors

    Visual Inspection: Check the wiring harnesses and connectors associated with the Low Speed CAN bus for any signs of damage, corrosion, or loose connections

  3. 3. Repair or Replace

    Repair any damaged wires or connectors and ensure all connections are secure

  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 3.5V when the bus is idle. If the voltage is consistently high, there may be a short circuit or a fault in the wiring

  5. 5. Check for Short Circuits

    Inspect the CAN bus wiring for any shorts to power or ground. This can cause the high voltage condition. Use a multimeter to check for continuity between the CAN wires and power/ground

  6. 6. Inspect Modules on the CAN Bus

    Identify all modules connected to the Low Speed CAN bus. Check for any malfunctioning modules that may be causing communication issues. Disconnecting modules one at a time can help isolate the problem

  7. 7. Test CAN Bus Termination Resistors

    Ensure that the termination resistors (typically 120 ohms) at both ends of the CAN bus are present and functioning correctly. A missing or faulty resistor can lead to communication issues

  8. 8. Check for Interference

    Look for sources of electrical interference that may be affecting the CAN bus communication. This can include aftermarket accessories or modifications that may be improperly installed

  9. 9. Scan for Module Communication

    Use a scan tool to check if all modules on the Low Speed CAN bus are communicating properly. If some modules are not responding, it may indicate a problem with that specific module or its connection

  10. 10. 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. Monitor the vehicle's performance and any warning lights

  11. 11. Seek Professional Help

    If you are unable to resolve the issue, consider seeking assistance from a professional mechanic or automotive technician who has experience with CAN bus systems. By following these steps, you should be able to diagnose and potentially resolve the U0023 code related to Low Speed CAN Communication Bus issues