P0117 means Engine Coolant Temperature Sensor 1 Circuit Low. The coolant temperature sensor signal is reading low voltage, which the computer interprets as a very hot engine or a shorted circuit. It is a generic OBD-II code, so the definition is the same on any make, but the most likely cause varies by engine; confirm with a scan tool and the service information for your vehicle before buying parts.
What P0117 means
The coolant temperature reading feeds many systems: warm-up fueling, ignition timing, idle speed, cooling fan control, transmission shift timing and often the dash gauge. A wrong reading causes symptoms far beyond the cooling system, and a real overheat can damage an engine quickly. Confirm the actual temperature with a scan tool or an infrared thermometer before replacing parts.
P0117 symptoms
- Cooling fans running constantly
- Hard starting when cold, or rich running
- Incorrect temperature gauge reading on some vehicles
Common causes of P0117
- Shorted sensor or wiring
- Damaged connector
- Failed sensor
How to diagnose P0117
- Compare the scan tool coolant temperature with the real engine temperature
- Inspect the connector and wiring for shorts
- Test the sensor resistance against the specification
Can you drive with P0117?
Possible, but the computer may run the fans and enrich fueling. Confirm the engine is not actually overheating before driving.
P0117 tips
A scan tool reading far hotter than the engine could be, on a cold engine, points to a short in the wiring or the sensor. If the reading matches the real temperature when you look, the fault is intermittent; wiggle the harness while watching live data to find it.
Will P0117 clear itself?
If the fault stops, the computer turns off the check engine light by itself after several drive cycles without seeing it again, and the code stays in memory as history for a while. Clearing P0117 with a scan tool after a repair is fine, but if the cause is still there the code returns, sometimes within one drive. Disconnecting the battery also clears codes on most vehicles, but it erases learned fuel trims and idle settings as well.
Related codes
| Code | Meaning |
|---|---|
| P0118 | Engine Coolant Temperature Sensor 1 Circuit High |
| P0128 | Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature) |
| P0217 | Engine Coolant Over Temperature Condition |
Guides that help
- coolant temperature sensor
- engine overheating
- water pump and thermostat symptoms
- radiator fan not working
When it is more than a sensor
Most cooling codes end with a thermostat, sensor, fan or leak repair. If the engine overheated badly enough to fail the head gasket or warp the heads, compare a repair against a replacement on our engines page and read engine replacement cost.
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