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B1255 Air Temperature External Sensor Circuit Open

The OBD2 code B1255 indicates that there is an open circuit in the external air temperature sensor, meaning the sensor is not receiving power or is disconnected, leading to a failure in reading the air temperature

Definition

The OBD2 code B1255 indicates that there is an open circuit in the external air temperature sensor, meaning the sensor is not receiving power or is disconnected, leading to a failure in reading the air temperature

Common causes

  • Damaged or frayed wiring
  • Poor electrical connections
  • Faulty air temperature sensor
  • Corroded connectors
  • Open circuit in the wiring harness
  • Short circuit in the wiring
  • Faulty engine control module (ECM)

Common misdiagnoses

  • Faulty air temperature sensor
  • Wiring issues or shorts in the circuit
  • Malfunctioning engine control module (ECM)
  • Incorrectly diagnosed as a coolant temperature sensor issue
  • Air conditioning system problems
  • Issues with the ambient temperature sensor
  • Faulty connectors or terminals in the circuit

Troubleshooting steps

  1. 1. Understand the Code

    B1255 typically refers to a problem with the external air temperature sensor circuit, which may be open or disconnected. This sensor is often used by the vehicle's engine control unit (ECU) to monitor ambient air temperature for various functions

  2. 2. Visual Inspection

    Check the Wiring and Connectors

  3. 3. Inspect the wiring harness connected to the air temperature sensor for any signs of damage, fraying, or corrosion

  4. 4. Ensure that the connectors are securely attached and free of dirt or moisture

  5. 5. Test the Sensor: Measure Resistance

  6. 6. Disconnect the air temperature sensor and use a multimeter to measure the resistance across the sensor terminals. Compare the readings to the specifications in the vehicle’s service manual

  7. 7. Check for Shorts

  8. 8. With the sensor disconnected, check for continuity in the wiring to ensure there are no shorts to ground or power

  9. 9. Check the Circuit: Inspect the Circuit

  10. 10. Use a multimeter to check for continuity in the circuit from the sensor to the ECU. Look for any breaks or opens in the wiring

  11. 11. Power and Ground

  12. 12. Verify that the sensor is receiving the correct voltage and ground. Check the voltage at the sensor connector with the ignition on

  13. 13. Test the ECU

    If the sensor and wiring appear to be in good condition, the issue may lie with the ECU itself. Check for any software updates or known issues with the ECU related to this code

  14. 14. Clear the Code

    After performing the above checks and repairs, clear the trouble code using an OBD-II scanner and take the vehicle for a test drive to see if the code returns

  15. 15. Consult Technical Resources

    If the problem persists, consult the vehicle’s service manual or technical resources for specific diagnostic procedures related to the B1255 code

  16. 16. Seek Professional Help

    If you are unable to resolve the issue after following these steps, it may be best to consult a professional mechanic or technician who has experience with your specific vehicle make and model.Additional Tips: - Always ensure that you are working safely and disconnect the battery when working on electrical components. - Keep in mind that environmental factors, such as extreme temperatures, can also affect sensor readings. By following these troubleshooting steps, you should be able to identify and resolve the issue related to the B1255 code