P0125 – Insufficient Coolant Temperature for Closed Loop
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Symptoms
- Poor fuel economy
- Slow warmup
- Heater not warm
- Check engine light
- Slight rough idle
Causes
- Stuck open thermostat
- Low coolant
- Faulty coolant temp sensor
- Cooling fan stuck on
- Air in cooling system
Diagnosis
- Check coolant level
- Inspect thermostat
- Test coolant temp sensor
- Check fan operation
- Bleed cooling system
Repair
- Replace thermostat
- Refill coolant
- Replace temp sensor
- Repair fan issue
- Bleed cooling system