WOMS
U code network High severity

U0026 Low Speed CAN Communication Bus (-) High

The OBD2 code U0026 indicates a problem with the low-speed CAN communication bus, specifically that the signal is high, which may suggest a fault in the communication between modules or a wiring issue

Definition

The OBD2 code U0026 indicates a problem with the low-speed CAN communication bus, specifically that the signal is high, 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 control module
  • Poor ground connection
  • Interference from other electrical components
  • Corroded or damaged connectors
  • Faulty termination resistors
  • Software issues in the control modules
  • Low battery voltage or power supply issues

Common misdiagnoses

  • Faulty CAN bus wiring
  • Defective control modules
  • Poor ground connections
  • Faulty sensors
  • Corroded connectors
  • Low battery voltage
  • Intermittent electrical issues
  • Software glitches in modules

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 related issues

  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. Connector Pins

    Ensure that the pins in the connectors are not bent, corroded, or pushed back

  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. If the voltage is significantly higher, it may indicate a short or a fault

  5. 5. Check for Short Circuits

    Inspect the CAN bus wiring for any shorts to power or ground. A short circuit can cause the signal to be high

  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

  7. 7. Disconnect each module one at a time to see if the code clears or changes, indicating which module may be faulty

  8. 8. Test the CAN Bus with an Oscilloscope

    If available, use an oscilloscope to monitor the CAN bus signals. This can help identify if the signals are being transmitted correctly and if there are any anomalies

  9. 9. Check for Interference

    Look for any sources of electrical interference that may be affecting the CAN bus communication, such as aftermarket accessories or modifications

  10. 10. Inspect Ground Connections

    Ensure that all ground connections related to the CAN bus are secure and free of corrosion. Poor grounding can lead to communication issues

  11. 11. Check for Software Updates

    Sometimes, a software update for the vehicle’s modules can resolve communication issues. Check with the manufacturer for any available updates

  12. 12. 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

  13. 13. Consult a Professional

    If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or technician with experience in automotive electronics and CAN bus systems. By following these troubleshooting steps, you should be able to identify and resolve the issue related to the U0026 code