OBD codes / P0118
P0118
ModerateEngine Coolant Temperature (ECT) Sensor Circuit High
P0118 is usually safe to drive with briefly, but don't ignore it — a false cold reading makes the engine run rich and can prevent the cooling fans from coming on, which risks overheating in traffic or hot weather. Get it diagnosed soon, and watch the temperature if you're driving in the meantime.
What this code means
The engine coolant temperature (ECT) sensor tells the computer how hot the engine is, which affects fueling, cooling-fan operation, and more. P0118 means that sensor's signal is reading high — which the computer interprets as extremely cold (or an open circuit). Usually it's a failed sensor or a break in its wiring/connector, and occasionally genuinely low coolant. A false "cold" reading makes the engine run rich and may keep the cooling fans from turning on when they should, so it's worth fixing.
Symptoms you might notice
- Check-engine light
- Rich running and reduced fuel economy
- Hard starting when warm
- Cooling fans not running or running constantly
- Inaccurate temperature gauge in some cars
What it costs to fix
Typical range: $40–$250 · about ~0.3–1.5 hrs of labor
| If the cause is… | Part | Labor |
|---|---|---|
| ECT sensor | $15–$80 | ~0.3–1 hrs |
| Wiring / connector repair | $10–$120 | ~0.5–1.5 hrs |
| Coolant top-up | $15–$60 | ~0.2–0.5 hrs |
The ECT sensor is inexpensive; cost is mostly access labor, which is low on most engines. Wiring repairs are cheap once the fault is found. A genuinely low coolant level points to a separate leak worth checking.
The price swings on which cause it turns out to be — so confirm the cause before paying. Diagnose P0118 for my exact vehicle →
Frequently asked
Can I drive with P0118?
Short-term usually yes, but keep an eye on the temperature gauge — a false cold reading can stop the cooling fans from running, raising overheating risk in traffic or heat. Get it fixed soon rather than letting it ride.
What does "circuit high" mean for P0118?
The sensor's voltage is at the high end, which the computer reads as extremely cold or disconnected. That points to a failed sensor or an open (broken) wire rather than a real temperature.
Can P0118 cause overheating?
Indirectly — if the computer thinks the engine is cold, it may not switch the cooling fans on when needed. The engine isn't actually cold, so it can overheat. That's why it's worth fixing promptly even though the car runs.
How much does it cost to fix P0118?
Usually inexpensive — the ECT sensor is cheap and easy to reach on most engines, and wiring repairs are modest. Confirm the wiring before replacing the sensor.
Seeing P0118 on your car? Get a diagnosis specific to your exact year, make and model.
Diagnose P0118 for my vehicleGeneric OBD-II reference. Manufacturer-specific behavior varies — confirm with a scan tool and, for safety-related codes, a professional inspection.