WOMS
U code network Medium severity

U1138 Lost Communication with Fuel Level Sensor

The OBD2 code U1138 indicates a loss of communication between the vehicle's control module and the fuel level sensor, which may affect the accurate reading of the fuel level

Definition

The OBD2 code U1138 indicates a loss of communication between the vehicle's control module and the fuel level sensor, which may affect the accurate reading of the fuel level

Common causes

  • Faulty fuel level sensor
  • Damaged wiring or connectors
  • Poor electrical connections
  • Failed fuel pump module
  • Malfunctioning engine control module (ECM)
  • Corroded terminals
  • Short circuit in the wiring harness
  • Software issues in the ECM

Common misdiagnoses

  • Faulty fuel level sensor
  • Wiring issues or shorts in the harness
  • Faulty engine control module (ECM)
  • Corroded connectors
  • Fuel gauge malfunction
  • Instrument cluster issues
  • Grounding problems
  • Faulty fuel pump module

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 and help identify related issues

  2. 2. Inspect the Fuel Level Sensor

    Location: The fuel level sensor is typically located in the fuel tank

  3. 3. Visual Inspection

    Check for any visible damage to the sensor or its wiring. Look for frayed wires, corrosion, or loose connections

  4. 4. Check Electrical Connections

    Connector Inspection: Ensure that the electrical connectors to the fuel level sensor are secure and free of corrosion

  5. 5. Wiring

    Inspect the wiring harness for any signs of wear, damage, or shorts

  6. 6. Test the Fuel Level Sensor

    Resistance Test: Use a multimeter to measure the resistance of the fuel level sensor. Compare the readings to the specifications in the vehicle’s service manual

  7. 7. Functionality Test

    If possible, test the sensor by applying a known voltage and checking the output signal

  8. 8. Check the Fuel Pump Module

    In some vehicles, the fuel level sensor is part of the fuel pump module. Ensure that the entire module is functioning correctly

  9. 9. Inspect the Instrument Cluster

    Sometimes, the issue may lie within the instrument cluster or the body control module (BCM). Check for any faults in these components

  10. 10. Check for Ground Issues

    Ensure that the ground connections for the fuel level sensor and related components are secure and free of corrosion

  11. 11. Scan for Communication Issues

    Use a scan tool to check for communication between the fuel level sensor and the vehicle’s computer. Look for any communication errors

  12. 12. Check for Software Updates

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

  13. 13. 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

  14. 14. Consult a Professional

    If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or technician who has access to advanced diagnostic tools.Conclusion By following these troubleshooting steps, you can systematically identify and address the cause of the U1138 code. Always refer to the specific service manual for your vehicle for detailed procedures and specifications