WOMS
P code powertrain Medium severity

P1438 A/C Evaporator Air Temperature Circuit Range/Performance

The OBD2 code P1438 indicates that the A/C evaporator air temperature sensor is reporting a temperature that is outside the expected range or performance parameters, which may affect the air conditioning system's...

Definition

The OBD2 code P1438 indicates that the A/C evaporator air temperature sensor is reporting a temperature that is outside the expected range or performance parameters, which may affect the air conditioning system's efficiency

Common causes

  • Faulty A/C evaporator temperature sensor
  • Wiring issues (shorts, opens, or corrosion)
  • Poor electrical connections
  • Faulty A/C control module
  • Refrigerant level issues (too low or too high)
  • A/C system leaks
  • Blocked or restricted airflow
  • Malfunctioning A/C compressor

Common misdiagnoses

  • Faulty A/C compressor
  • Refrigerant leaks
  • Blocked or restricted A/C system
  • Faulty A/C control module
  • Wiring issues or shorts in the circuit
  • Faulty temperature sensor
  • Incorrect A/C system charge
  • HVAC control head 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 help identify if there are related issues that need to be addressed

  2. 2. Inspect Wiring and Connectors

    Examine the wiring and connectors associated with the A/C evaporator temperature sensor. Look for signs of damage, corrosion, or loose connections that could affect the sensor's performance

  3. 3. Test the A/C Evaporator Temperature Sensor

  4. 4. Disconnect the sensor and test its resistance with a multimeter. Compare the readings to the specifications provided in the vehicle's service manual

  5. 5. If the resistance is outside the specified range, the sensor may be faulty and should be replaced

  6. 6. Check the A/C System

    Ensure that the A/C system is functioning properly. Low refrigerant levels, a malfunctioning compressor, or other A/C system issues can affect the temperature readings

  7. 7. Inspect the A/C Evaporator

    Check for any blockages or restrictions in the evaporator that could affect airflow and temperature readings. Ensure that the evaporator is clean and free of debris

  8. 8. Examine the Climate Control Module

    If the sensor and wiring are in good condition, the issue may lie within the climate control module or the vehicle's computer. Check for software updates or known issues related to the module

  9. 9. Clear Codes and Test Drive

    After performing the necessary repairs or replacements, clear the trouble codes and take the vehicle for a test drive to see if the code reappears

  10. 10. Consult Technical Service Bulletins (TSBs)

    Check for any TSBs related to the P1438 code for your specific vehicle make and model. Manufacturers may have issued guidance or fixes for known issues

  11. 11. Professional Diagnosis

    If the problem persists after performing the above steps, consider seeking help from a professional mechanic or technician who has experience with A/C systems and OBD-II diagnostics. By following these steps, you should be able to identify and resolve the issue related to the P1438 code