The engine takes too long to reach the temperature needed for closed loop fuel control. The driver may notice slow heat-up and higher consumption.
Likely causes, most common first
- Thermostat stuck open
- Low coolant level
- Faulty coolant temperature sensor
- Cooling fan running all the time
Parts usually involved
- Thermostat
- Coolant temperature sensor
- Coolant
Test before you replace
Check the coolant level and watch the live temperature rise from a cold start.
General guidance for generic OBD2 codes. Always follow the maker's procedure for the car in front of you.