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P code powertrain Medium severity

P1109 IAT - B Sensor Intermittent

The OBD2 code P1109 indicates an intermittent issue with the Intake Air Temperature (IAT) sensor B, which may affect the engine's air intake readings and performance

Definition

The OBD2 code P1109 indicates an intermittent issue with the Intake Air Temperature (IAT) sensor B, which may affect the engine's air intake readings and performance

Common causes

  • Faulty IAT sensor
  • Poor electrical connections or wiring issues
  • Corroded or damaged connectors
  • Short circuit in the wiring
  • Open circuit in the wiring
  • Faulty engine control module (ECM)
  • Intermittent sensor signal
  • Vacuum leaks affecting sensor readings

Common misdiagnoses

  • Faulty Mass Air Flow (MAF) Sensor
  • Faulty Engine Coolant Temperature (ECT) Sensor
  • Vacuum Leaks
  • Faulty Throttle Position Sensor (TPS)
  • Wiring or Connector Issues
  • Faulty Engine Control Module (ECM)
  • Clogged Air Filter
  • Intake Manifold Gasket Leaks

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 IAT Sensor

    Locate the IAT sensor, which is typically found in the intake manifold or air intake duct

  3. 3. Check for physical damage, corrosion, or loose connections at the sensor

  4. 4. Check Wiring and Connectors

    Inspect the wiring harness and connectors leading to the IAT sensor for any signs of wear, fraying, or damage

  5. 5. Ensure that all connections are secure and free of corrosion

  6. 6. Test the IAT Sensor

    Use a multimeter to test the resistance of the IAT sensor. Compare the readings to the specifications provided in the vehicle’s service manual

  7. 7. If the readings are outside the specified range, the sensor may be faulty and should be replaced

  8. 8. Check for Air Leaks

    Inspect the intake system for any air leaks that could affect the IAT readings. Look for cracks or loose fittings in hoses and the intake manifold

  9. 9. Inspect the Engine Coolant Temperature (ECT) Sensor

    Since the IAT and ECT sensors can sometimes affect each other, check the ECT sensor for proper operation. A faulty ECT sensor can lead to incorrect readings and trigger the P1109 code

  10. 10. Check the ECM

    If all other components are functioning correctly, the issue may lie with the engine control module itself. Ensure that the ECM is receiving the correct signals and is functioning properly

  11. 11. Clear the Code and Test Drive

    After performing repairs or replacements, clear the trouble codes using the OBD-II scanner

  12. 12. Take the vehicle for a test drive to see if the code reappears. Monitor the IAT readings during the drive to ensure they are within the expected range

  13. 13. Consult a Professional

    If the issue persists after following these steps, it may be beneficial to consult a professional mechanic or technician who can perform more advanced diagnostics. By following these troubleshooting steps, you should be able to identify and resolve the issue related to the P1109 code