Coolant temperature is too low for stable engine operation.
SYMPTOMS
- Check-engine light
- Long warm-up
- Weak cabin heat
LIKELY CAUSES
- Thermostat stuck open
- Faulty ECT sensor
- Low coolant
DIAGNOSIS STEPS
- Verify coolant level and warm-up curve
- Test thermostat
- Verify ECT sensor
RELATED PARTS
- Thermostat
- ECT sensor