P1118: Manifold Absolute Temperature Circuit Low Input

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. 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. Inspect the MAT Sensor
3. Locate the MAT sensor, which is usually found on or near the intake manifold
4. Check for physical damage to the sensor or its connector
5. Ensure that the sensor is properly seated and connected
6. Test the MAT Sensor
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. If the resistance is outside the specified range, the sensor may be faulty and should be replaced
9. Check the Wiring and Connectors
10. Inspect the wiring harness and connectors for any signs of damage, corrosion, or loose connections
11. Look for frayed wires, broken connectors, or any other issues that could affect the signal to the ECM
12. Test the Voltage Supply
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. If the voltage is low or absent, trace the wiring back to the ECM to identify any breaks or shorts
15. Check Ground Connections
16. Ensure that the ground connection for the MAT sensor is secure and free of corrosion
17. A poor ground can lead to incorrect sensor readings
18. Inspect the ECM
19. If all other components check out, there may be an issue with the ECM itself. This is less common but can happen
20. Check for any software updates or recalls related to the ECM
21. Clear the Code and Test Drive
22. After performing repairs or replacements, clear the trouble codes using the OBD-II scanner
23. Take the vehicle for a test drive to see if the code returns
24. Consult a Professional
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

Definition

Common causes

Common misdiagnoses

Troubleshooting steps

1. Check the Code

2. Inspect the MAT Sensor

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

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

5. Ensure that the sensor is properly seated and connected

6. Test the MAT Sensor

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

9. Check the Wiring and Connectors

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

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

12. Test the Voltage Supply

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

15. Check Ground Connections

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

17. A poor ground can lead to incorrect sensor readings

18. Inspect the ECM

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

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

21. Clear the Code and Test Drive

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

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

24. Consult a Professional

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