P0117
P0117 Engine Coolant Temperature Circuit Low Input
P0117 is a generic OBD2 powertrain diagnostic trouble code for engine coolant temperature circuit low input. The code identifies the system or circuit the engine computer flagged, but diagnosis still depends on vehicle symptoms, freeze-frame data, and related codes.
How urgent is P0117?
Cooling-system codes should be checked soon because overheating can quickly turn into major engine damage.
Common symptoms
- Check engine light
- Temperature gauge abnormal
- Weak cabin heat
- Cooling fans running unusually
- Poor fuel economy
Likely causes
- Low coolant
- Thermostat issue
- Coolant temperature sensor fault
- Cooling fan circuit fault
- Wiring or connector problem
What to check before replacing parts
1
Check coolant level cold
2
Inspect for leaks
3
Compare scan-tool temperature to actual temperature
4
Check fan command and relay operation
5
Inspect sensor wiring
Use the code with symptoms
A code points at the system, not always the failed part. Add your vehicle, mileage, symptoms, and whether the check engine light is steady or flashing so the AI diagnostic can narrow the next step.