What does P0117 mean?
The engine coolant temperature (ECT) sensor tells the computer how hot the engine is. It affects fuel mixture, idle speed, cooling fans and, on many cars, the temperature gauge.
Low voltage on a temperature sensor means the computer thinks it is very hot. This is nearly always a shorted sensor or wire.
Codes are a starting point. They tell you which test failed, not which part to replace. Check for other stored codes and fix those in a sensible order.
Symptoms
- Check engine light
- Hard starting
- Cooling fans running all the time (a common fail-safe)
- Poor fuel economy
- Wrong temperature gauge reading on some vehicles
Common causes
- Signal wire shorted to ground
- Sensor shorted internally
- Water in the connector
How to diagnose P0117
- Look at live data: a shorted sensor will read an impossibly hot temperature.
- Unplug the sensor. The reading should jump to a very cold value (around -40 F). If it does, the sensor is shorted; if it does not, the wiring is shorted to ground.
- Check sensor resistance against the service spec at a known temperature.
- Check the coolant level first (only when the engine is cold).
- Compare ECT with intake air temperature after an overnight cold soak.
How to fix it
- Top up or bleed the cooling system
- Repair wiring
- Replace the ECT sensor
Estimated repair cost
Likely repairs for P0117 run from about $80 to $250, depending on the cause.
| Repair | Typical range (parts + labor) |
|---|---|
| Diagnostic fee (scan + testing) | $100 - $200 |
| Coolant temperature sensor | $80 - $250 |
These are rough US estimates for an independent shop in 2026, based on typical parts prices and standard labor times. Dealers, big trucks, luxury brands and high-cost areas often run higher. They are not quotes. Use the repair cost estimator to adjust for your vehicle.
How serious is P0117?
Moderate severity
Usually drivable, but keep an eye on the real engine temperature. If it is overheating, stop.
P0117 FAQ
What does P0117 mean?
P0117 stands for "Engine Coolant Temperature Sensor 1 Circuit Low". The engine coolant temperature (ECT) sensor tells the computer how hot the engine is.
Can I drive with a P0117 code?
Usually drivable, but keep an eye on the real engine temperature. If it is overheating, stop.
How much does it cost to fix P0117?
It depends on the cause. The likely repairs for P0117 range from about $80 to $250 at an independent shop in the US, plus a diagnostic fee of roughly $100-$200. These are rough estimates; dealer prices and some vehicles run higher.
What is the most common cause of P0117?
The most common causes are: signal wire shorted to ground; sensor shorted internally; water in the connector.