OBD2 codes.
A code identifies a signal or system that needs to be checked, not a part you should replace.
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P0118Coolant temperature sensor signal highUrgency medium
Engine Coolant Temperature Sensor 1 Circuit High
This sensor tells the ECU how hot the engine is. With it the ECU adjusts the mixture, the idle, the fan and, on diesels, the glow plugs.
What the car has detected
The coolant temperature sensor signal is above its range. It is usually a broken wire, a loose connector or a faulty sensor.
The car may start badly when cold, run unevenly or show a temperature that is not the real one, so you might not notice if the engine overheats. Have it checked soon and keep an eye on the temperature.
Symptoms
- Engine warning light on
- Longer or harder starting
- High or uneven idle
- The temperature gauge suddenly drops and rises
- On diesels, the glow plug light stays on longer than usual
Possible causes
- Damaged sensor wiring or connector
- Faulty coolant temperature sensor
Checks for the garage
- Check the sensor connector and wiring
- Compare, with the diagnostic tool, the temperature the sensor reads with the real engine temperature
- Test or replace the coolant temperature sensor
Next step
Ask them to check the coolant temperature sensor wiring and connector and to test or replace the sensor.
Go to a garage soon. In the meantime, watch the temperature: if it rises a lot or steam comes out, stop somewhere safe and switch the engine off.