OBD-II · Engine and powertrain (P)
P0117
Engine coolant temperature circuit low input
What it means
The coolant temperature signal voltage is below its valid range, which the ECU would read as an extremely hot engine. This is usually a short to ground.
Symptoms
- cooling fan running all the time
- wrong or no temperature gauge reading
- hard starting, rough running or higher fuel consumption
- engine warning light
Likely causes, most likely first
| No. | Cause |
|---|---|
| 01 | short to ground |
| 02 | failed sensor |
| 03 | damaged wiring |
| 04 | connector contamination |
| 05 | ECU reference fault |
What to check, step by step
- 01Check the coolant level first
- 02Compare the coolant temperature in live data with outside air temperature after an overnight cold soak, then with the real warm engine temperature
- 03Inspect the sensor connector for corrosion and broken locking tabs
- 04Measure the sensor resistance against temperature and check the wiring to the ECU
- 05Replace the sensor (usually cheap) and bleed the cooling system afterwards