P0117 — Engine Coolant Temperature Sensor Circuit Low Input
Drive with caution — fix soon.
What P0117 means
This code is set when the engine coolant temperature sensor sends a signal that's too low, which the computer reads as an unusually hot engine. Because the ECU relies on this sensor to manage fuel, fans, and timing, a bad reading can cause the car to run rich and the cooling fans to behave oddly. The fault usually lies in the sensor, its wiring, or a short to ground.
Common symptoms
- Check Engine light is on
- Cooling fans running constantly
- Worse fuel economy from a rich mixture
- Black smoke or fuel smell in some cases
- Temperature gauge reading inaccurately
Common causes
- Faulty coolant temperature sensor
- Short to ground in the signal wiring
- Corroded or damaged sensor connector
- Wiring chafed against the engine
- Poor ground or reference voltage
- Incorrect or contaminated coolant affecting readings
Typical repair cost
$100 – $300
Varies by vehicle and root cause.
Frequently asked questions
Can I drive with a P0117 code?
For short distances, usually yes, but keep an eye on your temperature gauge. Since the sensor reading is unreliable, you can't fully trust the dashboard, so get it diagnosed soon.
How much does it cost to fix P0117?
Commonly $100 to $300. The coolant temp sensor itself is inexpensive; most of the cost is labor and any wiring repair needed.
Is P0117 serious?
It's a moderate concern. The engine usually still runs, but the false 'hot' reading can hurt fuel economy and mask a real overheating problem, so don't put it off.
Could P0117 mean my engine is actually overheating?
Not by itself. The code points to a low sensor signal, not real heat. Still, confirm with the temperature gauge and a scan tool, because a faulty sensor can hide a genuine cooling issue.