OBD-II · Engine and powertrain (P)
P0125
Insufficient coolant temperature for closed-loop fuel control
What it means
The engine takes too long to reach the temperature the ECU needs before it starts using the lambda sensor to control the mixture.
Symptoms
- temperature gauge slow to rise
- poor heater output in winter
- higher fuel consumption
- engine warning light
Likely causes, most likely first
| No. | Cause |
|---|---|
| 01 | thermostat stuck open |
| 02 | coolant temperature sensor reading low |
| 03 | low coolant level |
| 04 | cooling fan running all the time |
What to check, step by step
- 01Check the coolant level
- 02Watch the coolant temperature during a warm-up drive and compare with an infrared thermometer
- 03Check that the cooling fan is not running on a cold engine
- 04Replace the thermostat if the engine does not reach operating temperature