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P codepowertrainMedium severity

P1118Manifold Absolute Temperature Circuit Low Input

The OBD2 code P1118 indicates that the Manifold Absolute Temperature (MAT) sensor circuit is providing a low voltage input, suggesting a potential issue with the sensor or its wiring

Definition

The OBD2 code P1118 indicates that the Manifold Absolute Temperature (MAT) sensor circuit is providing a low voltage input, suggesting a potential issue with the sensor or its wiring

Common causes

  • Faulty manifold absolute temperature (MAT) sensor
  • Damaged wiring or connectors in the MAT circuit
  • Short circuit to ground in the MAT circuit
  • Open circuit in the MAT sensor wiring
  • Poor electrical connections
  • Faulty engine control module (ECM)

Common misdiagnoses

  • Faulty Manifold Absolute Temperature (MAT) sensor
  • Wiring issues or short circuits in the MAT circuit
  • Faulty Engine Control Module (ECM)
  • Vacuum leaks
  • Faulty intake air temperature sensor
  • Issues with the mass air flow (MAF) sensor
  • Problems with the throttle position sensor (TPS)
  • Engine overheating or cooling system issues

Troubleshooting steps

  1. 1.Check the Code

    Use an OBD-II scanner to confirm the P1118 code and check for any additional codes that may provide more context about the issue

  2. 2.Inspect the MAT Sensor

  3. 3.Locate the MAT sensor, which is usually found on or near the intake manifold

  4. 4.Check for physical damage to the sensor or its connector

  5. 5.Ensure that the sensor is properly seated and connected

  6. 6.Test the MAT Sensor

  7. 7.Use a multimeter to measure the resistance of the MAT sensor. Compare the readings to the specifications provided in the vehicle's service manual

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

  9. 9.Check the Wiring and Connectors

  10. 10.Inspect the wiring harness and connectors for any signs of damage, corrosion, or loose connections

  11. 11.Look for frayed wires, broken connectors, or any other issues that could affect the signal to the ECM

  12. 12.Test the Voltage Supply

  13. 13.With the ignition on (engine off), check the voltage at the MAT sensor connector. It should typically receive a reference voltage (usually around 5 volts)

  14. 14.If the voltage is low or absent, trace the wiring back to the ECM to identify any breaks or shorts

  15. 15.Check Ground Connections

  16. 16.Ensure that the ground connection for the MAT sensor is secure and free of corrosion

  17. 17.A poor ground can lead to incorrect sensor readings

  18. 18.Inspect the ECM

  19. 19.If all other components check out, there may be an issue with the ECM itself. This is less common but can happen

  20. 20.Check for any software updates or recalls related to the ECM

  21. 21.Clear the Code and Test Drive

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

  23. 23.Take the vehicle for a test drive to see if the code returns

  24. 24.Consult a Professional

  25. 25.If the issue persists after following these steps, it may be best to consult a professional mechanic for further diagnosis. By following these troubleshooting steps, you should be able to identify and resolve the issue related to the P1118 code