P0117 Engine Coolant Temperature Circuit Low
P0117 is a generic OBD2 powertrain code. It means “Engine Coolant Temperature Circuit Low” — the same on every make and model, because the definition comes from the SAE J2012 standard rather than from the carmaker.
Ask the AI about P0117 on your car- System
- Powertrain (P)
- Code type
- Generic (SAE)
- Range
- P01xx
- Urgency
- Moderate
What P0117 means
The engine coolant temperature (ECT) sensor tells the computer how warm the engine is — for the fuel mixture, idle speed, the radiator fan and often the dashboard gauge. The computer found its signal too high, so it reads implausibly cold (P0118, often an open circuit), too low, so it reads implausibly hot (P0117), implausible (P0116), or a circuit fault (P0115).
Symptoms
- The radiator fan running constantly — the computer’s fail-safe
- Hard starting, a rough idle or black smoke
- A temperature gauge that reads wrong or not at all
- Worse fuel economy
Most likely causes
- A failed sensor
- A corroded or loose connector
- Damaged wiring
- Low coolant leaving the sensor in an air pocket (P0116)
What to check first
- Check the coolant level first, with the engine cold
- On a cold engine, compare the reported coolant temperature with the outside temperature — they should be close
- Inspect the connector, then replace the sensor — usually an inexpensive part
Can I keep driving with P0117?
Drivable — plan the repair soon
Carefully. The gauge may be wrong, so you might not see a real overheat coming: check the coolant level, watch for steam or a sweet smell, and get it fixed within days.
What the wording tells you
“Low” here is electrical: the module saw the voltage in this circuit stay below its expected window. The usual causes are a short to ground, a broken signal or reference wire, a corroded connector — or the component itself.
How P0117 breaks down
Powertrain. Engine, transmission, fuel and emissions — the codes behind the check engine lamp.
Generic code: defined by SAE, the same on every make.
Fuel & air metering.
The specific fault within this range.
Where to look: Fuel & air metering
The sensors the engine computer meters fuel from — mass air flow, manifold pressure, intake air and coolant temperature, throttle position, oxygen sensors and fuel pressure — the fuel trims it learns from them, and the injector, fuel-pump and turbocharger circuits.
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Frequently asked
What does P0117 mean?
P0117 is a generic OBD2 powertrain code. It means “Engine Coolant Temperature Circuit Low” — the same on every make and model, because the definition comes from the SAE J2012 standard rather than from the carmaker. The engine coolant temperature (ECT) sensor tells the computer how warm the engine is — for the fuel mixture, idle speed, the radiator fan and often the dashboard gauge. The computer found its signal too high, so it reads implausibly cold (P0118, often an open circuit), too low, so it reads implausibly hot (P0117), implausible (P0116), or a circuit fault (P0115).
Can I drive with P0117?
Carefully. The gauge may be wrong, so you might not see a real overheat coming: check the coolant level, watch for steam or a sweet smell, and get it fixed within days.
What causes P0117?
A failed sensor; A corroded or loose connector; Damaged wiring; Low coolant leaving the sensor in an air pocket (P0116).
How do I clear P0117?
Fix the cause first, then clear it with any OBD2 scanner or app. Once the fault is gone the car also clears it on its own: the check engine lamp goes off after the self-test passes on three drive cycles in a row, and the stored code ages out after about 40 warm-ups. Clearing without a repair only hides it for a while — and resets the readiness monitors an emissions inspection looks at.
Is P0117 the same on every car?
Yes. P0117 is a generic SAE J2012 code, so its definition is identical on every make and model. What differs is the cause behind it and the repair procedure, which depend on the engine — that’s why the assistant on this page asks for your car.
Guides
Definitions: the generic SAE J2012 codes from Brimly’s offline dictionary (data version 2026.09). Causes and advice are general guidance for all makes — the service information for your car has the last word.