P0118: Engine Coolant Temperature Circuit High Input

Definition

The OBD2 code P0118 indicates that the engine coolant temperature sensor is sending a high voltage signal, suggesting that the engine coolant temperature is higher than expected or that there is a fault in the sensor or its circuit

Common causes

Faulty engine coolant temperature sensor
Open or shorted wiring in the coolant temperature sensor circuit
Poor electrical connections or corroded connectors
Faulty engine control module (ECM)
High resistance in the wiring harness
Incorrectly installed or damaged coolant temperature sensor
Engine overheating conditions

Common misdiagnoses

Faulty Engine Coolant Temperature Sensor
Wiring Issues or Short Circuits
Engine Control Module (ECM) Malfunction
Thermostat Failure
Coolant Leaks
Air in the Cooling System
Faulty Temperature Gauge or Display
Incorrect Coolant Type or Mixture

Troubleshooting steps

1. Check for Additional Codes

Before proceeding, check for any other related trouble codes that may provide more context to the problem
2. Inspect the ECT Sensor
3. Locate the ECT sensor, which is usually found near the thermostat housing or on the engine block
4. Check for physical damage, corrosion, or loose connections at the sensor
5. Test the ECT Sensor
6. Use a multimeter to measure the resistance of the ECT sensor at various temperatures. Compare the readings to the manufacturer's specifications
7. If the resistance is out of range, the sensor may need to be replaced
8. Check the Wiring and Connectors
9. Inspect the wiring harness and connectors leading to the ECT sensor for any signs of damage, fraying, or corrosion
10. Ensure that all connections are secure and free of moisture
11. Test the Voltage Supply
12. With the ignition on (engine off), check the voltage at the ECT sensor connector. It should typically be around 5 volts (check the specific vehicle's service manual for exact values)
13. If the voltage is too high, there may be a short circuit in the wiring
14. Check for Ground Issues
15. Ensure that the ECT sensor has a good ground connection. A poor ground can cause incorrect readings
16. Use a multimeter to check for continuity between the sensor ground and the vehicle ground
17. Inspect the Engine Control Module (ECM)
18. If all other components check out, there may be an issue with the ECM itself. This is less common but can happen
19. Check for any software updates or recalls related to the ECM
20. Clear the Code and Test Drive
21. After performing repairs or replacements, clear the trouble code using an OBD-II scanner
22. Take the vehicle for a test drive to see if the code returns
23. Consult the Service Manual
24. If the issue persists, refer to the vehicle's service manual for specific diagnostic procedures and specifications related to the ECT sensor and its circuit
25. Seek Professional Help
26. If you are unable to resolve the issue after these steps, it may be best to consult a professional mechanic for further diagnosis. By following these steps, you should be able to identify and resolve the issue causing the P0118 code

Definition

Common causes

Common misdiagnoses

Troubleshooting steps

1. Check for Additional Codes

2. Inspect the ECT Sensor

3. Locate the ECT sensor, which is usually found near the thermostat housing or on the engine block

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

5. Test the ECT Sensor

6. Use a multimeter to measure the resistance of the ECT sensor at various temperatures. Compare the readings to the manufacturer's specifications

7. If the resistance is out of range, the sensor may need to be replaced

8. Check the Wiring and Connectors

9. Inspect the wiring harness and connectors leading to the ECT sensor for any signs of damage, fraying, or corrosion

10. Ensure that all connections are secure and free of moisture

11. Test the Voltage Supply

12. With the ignition on (engine off), check the voltage at the ECT sensor connector. It should typically be around 5 volts (check the specific vehicle's service manual for exact values)

13. If the voltage is too high, there may be a short circuit in the wiring

14. Check for Ground Issues

15. Ensure that the ECT sensor has a good ground connection. A poor ground can cause incorrect readings

16. Use a multimeter to check for continuity between the sensor ground and the vehicle ground

17. Inspect the Engine Control Module (ECM)

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

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

20. Clear the Code and Test Drive

21. After performing repairs or replacements, clear the trouble code using an OBD-II scanner

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

23. Consult the Service Manual

24. If the issue persists, refer to the vehicle's service manual for specific diagnostic procedures and specifications related to the ECT sensor and its circuit

25. Seek Professional Help

26. If you are unable to resolve the issue after these steps, it may be best to consult a professional mechanic for further diagnosis. By following these steps, you should be able to identify and resolve the issue causing the P0118 code