Cooling system
P0117 — Engine Coolant Temperature Circuit Low
The coolant temperature sensor signal is lower than normal, which the ECU reads as extremely hot coolant. It may run the fan constantly and enrich the mixture.
Common causes
- Faulty ECT sensor
- Signal wire shorted to ground
- Damaged or wet connector
- Wiring harness fault
- Faulty engine control module (rare)
Symptoms
- Cooling fan runs all the time
- Hard starting when cold
- Higher fuel consumption
- Check engine light
How to check
- Check the ECT connector and wiring for a short to ground
- Read the live value; an unrealistically high temperature with a cold engine suggests this fault
- Measure the sensor resistance and compare it with the specification
- Replace the sensor if it is out of specification
Can you keep driving?
Usually drivable, but the engine may run rich and the fan may stay on. Check the real temperature gauge and fix it soon.
Related codes
Frequently asked questions
- What does P0117 mean?
- The ECT sensor circuit voltage is low, as if the coolant were extremely hot.
- Why does my fan run constantly with P0117?
- The ECU believes the engine is overheating, so it keeps the fan on as protection.
General reference information. It does not replace a diagnosis on your own vehicle. The same code can have different causes depending on make, model year and engine; check the manufacturer's documentation or ask a technician with a scan tool.