P0118 — Engine Coolant Temperature Sensor Circuit High Input
Drivable short-term, but fix now to avoid damage.
What P0118 means
This code appears when the coolant temperature sensor signal reads too high, which the computer interprets as a cold engine even after it has warmed up. Because the ECU may not command the cooling fans correctly and keeps the mixture rich, this fault can lead to actual overheating. It usually stems from a bad sensor, an open circuit, or a wiring problem.
Common symptoms
- Check Engine light is on
- Engine running rich and poor fuel economy
- Cooling fans not turning on when they should
- Possible overheating in traffic or on hot days
- Temperature gauge stuck low or reading cold
Common causes
- Faulty coolant temperature sensor
- Open circuit or broken signal wire
- Corroded or disconnected sensor connector
- High resistance in the wiring
- Poor ground connection
- Low coolant level exposing the sensor to air
Typical repair cost
$100 – $350
Varies by vehicle and root cause.
Frequently asked questions
Can I drive with a P0118 code?
Only if you must, and watch the temperature gauge closely. The cooling fans may not run correctly, so the engine can overheat, which can cause expensive damage. Get it fixed quickly.
How much does it cost to fix P0118?
Usually $100 to $350. The sensor is cheap, but diagnosing and repairing wiring or a connector, plus labor, raises the total.
Is P0118 serious?
It can be. Because it may stop the cooling fans from running and keep the engine running rich, there's a real overheating risk, so treat it as a high priority.
Why might my engine overheat with P0118?
The sensor falsely reports a cold engine, so the computer may not turn on the cooling fans. Without the fans, the engine can overheat, especially in slow traffic or hot weather.