P0125 – Insufficient Coolant Temperature for Closed Loop
Description
The ECM detects that coolant temperature does not reach the required level for closed-loop fuel control.
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Compare Diagnostic ScannersSymptoms
- Long warm-up time
- Poor fuel economy
- Rough idle
- Reduced heater performance
Causes
- Stuck-open thermostat
- Low coolant level
- Faulty ECT sensor
- Cooling system issues
Diagnosis
- Check coolant level and leaks
- Monitor ECT temperature rise vs time
- Compare ECT to infrared thermometer
- Inspect thermostat operation
Repair
- Replace thermostat if stuck open
- Refill and bleed cooling system
- Repair leaks
- Replace ECT sensor if readings are inaccurate
