OBD-II diagnostic trouble code
P0117Caution
Engine Coolant Temperature Circuit Low Input
The coolant temperature sensor's signal to the computer is reading lower than physically possible — essentially, the computer thinks the engine is far colder than it really is, which usually means an electrical fault rather than an actual cooling problem.
Symptoms
- Cooling fan may run constantly, even with a cold engine
- Poor fuel economy — the computer keeps running a cold-start-style rich mixture
- Rough idle, especially after the engine has warmed up
- Temperature gauge (if it reads directly from this sensor) may sit unusually low or peg at maximum
Likely causes
- Short circuit to ground in the sensor's wiring — the most common cause of a "low input" fault specifically
- Failed coolant temperature sensor itself
- Corroded or damaged connector at the sensor
How to diagnose it
- Check the sensor connector for corrosion, moisture, or damage
- Test the sensor's resistance at different (known) temperatures against the spec table in the service manual
- Check the wiring harness for a short to ground between the sensor and the ECU if the sensor itself tests fine
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Code names are compiled from open/standardized SAE and ISO references. Explanations, symptoms, causes and fixes are original. Covers generic (P0/C0/B0/U0) codes only — manufacturer-specific codes are planned for a future update.
Frequently asked questions
Can I drive with P0117?
You can usually keep driving with P0117, but don't put it off — the underlying cause can get worse or lead to further damage the longer it goes unaddressed. Get it diagnosed as soon as you reasonably can.
How much does it cost to fix P0117?
Typical repair costs for {code} range from roughly 40 to 250 EUR, depending on the specific cause and your car — see the fixes listed above for a breakdown.
What causes P0117?
Short circuit to ground in the sensor's wiring — the most common cause of a "low input" fault specifically Failed coolant temperature sensor itself Corroded or damaged connector at the sensor
Reviewed by Artyom SemenovAutomotive Editor · Fact-checked by Yauheni Kapliarchuk, Editor-in-Chief