The engine is not reaching normal operating temperature within the expected time — the thermostat is staying open.
SYMPTOMS
- Check-engine light
- Long warm-up
- Low temp gauge on the highway
- Weak cabin heat
- Worse economy/emissions
LIKELY CAUSES
- Thermostat stuck open (most common)
- Faulty ECT sensor
- Low coolant
- Faulty IAT reference
DIAGNOSIS STEPS
- Monitor the warm-up curve
- Verify coolant level
- Test thermostat opening temperature
- Verify ECT/IAT
RELATED PARTS
- Thermostat
- ECT sensor
- Coolant