P0125
PowertrainTemperature Sensormoderate severityInsufficient Coolant Temperature for Closed Loop Fuel Control
What P0125 Means
The engine is not reaching normal operating temperature quickly enough for the PCM to enter closed-loop fuel control.
Symptoms
- Check Engine Light
- Poor fuel economy
- Extended warmup time
- Rich exhaust smell
Common Causes
- Stuck-open thermostat
- Faulty ECT sensor
- Cooling fan running constantly
- Low coolant level
Diagnostic Steps
- Monitor ECT warmup time (should reach 160°F within 5-10 min)
- Test thermostat
- Check cooling fan operation
- Test ECT sensor
Where to start: Replace thermostat. Most common cause.
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