P0118 — Engine coolant temperature (ECT) sensor circuit high input

What this code generally means, its most common causes, and how serious it is.

TYPE: GENERICSYSTEM: AIR-FUEL MIXTURE

What does the code P0118 mean?

The engine coolant temperature (ECT) sensor is sending a signal that corresponds to an implausibly high temperature — often an open circuit — even when the engine is cold.

Common possible causes

Damaged or disconnected wiring — the most common cause of an open circuit.
A corroded connector — poor contact at the sensor.
A failing ECT sensor — a consistently wrong reading.

General severity

Moderate — worth checking soon

As with P0117, this sensor affects the cooling fan and fuel metering — a wrong reading in either direction is worth checking soon rather than ignoring.

This is still a general severity for this code, not a diagnostic for your car. Only a real read of your codes, with your mileage and vehicle history, can tell what's really going on.

Get a diagnostic for YOUR car

Connect a Bluetooth OBD2 reader and read your vehicle's real codes with Meca — free, no appointment, with causes ranked for your actual situation.

🔌 Read my OBD2 codes

Meca doesn't replace an in-person check by a professional. For any serious sign (a flashing light, a major loss of power, a fuel smell), see a mechanic promptly.

Frequently asked questions

Does the fan run constantly with this code?

That's possible on some vehicles, if the module thinks the engine is always hot because of the wrong signal — but it isn't guaranteed on every model.

Is this the same sensor as P0117?

Yes, it's the same sensor (ECT): P0117 signals a reading that's too low, P0118 signals one that's too high.

Can I drive with this code?

Usually yes short-term, but a check is still advisable to avoid an effect on starting or fan management.