P0117 — Engine coolant temperature (ECT) sensor circuit low input

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

TYPE: GENERICSYSTEM: AIR-FUEL MIXTURE

What does the code P0117 mean?

The engine coolant temperature (ECT) sensor is sending a signal that corresponds to an implausibly low temperature — often close to a short circuit — even when the engine is warm.

Common possible causes

A short in the wiring or a corroded connector — the most common cause of an implausibly low signal.
A failing ECT sensor — the internal element gives a consistently wrong reading.
A poor ground connection — affects the sensor's electrical reading.

General severity

Moderate — worth checking soon

This sensor affects cold-start fuel metering, the cooling fan, and sometimes the dashboard temperature gauge. A wrong reading can cause hard cold starts or keep the fan from engaging correctly — worth checking soon.

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.

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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

Can this cause overheating?

Indirectly, yes: if the module thinks the engine is always cold, the cooling fan may not turn on when it should. That's one reason not to ignore this code.

My temperature gauge looks off — is that related?

Possibly — on many vehicles, the same reading feeds both the control module and the dashboard gauge.

Is this an easy sensor to replace?

It depends on the vehicle and how accessible it is. Meca doesn't replace a mechanic's judgment for that kind of repair.