Insufficient Coolant Temperature for Closed Loop Fuel Control
With the engine cold the ECU uses a richer mixture. When the coolant reaches a certain temperature it starts adjusting the mixture with the lambda sensor.
What the car has detected
The coolant has not reached the temperature needed in the time the ECU expects.
It is not dangerous, but the car uses more fuel, heats the cabin poorly and the engine wears more if it always runs cold. Have it checked when you can.
Symptoms
- Engine warning light on
- The heater takes a long time to warm up
- The temperature gauge stays low
Possible causes
- Thermostat stuck open
- Faulty coolant temperature sensor
- Low coolant
Checks for the garage
- Check the coolant level with the engine cold
- Watch in live data how the temperature rises as it warms up
- Check the thermostat
Next step
Ask for the thermostat, the most common cause, and the temperature sensor to be checked.
You can keep using the car and book a visit without hurry. Replacing the thermostat is a routine garage job.