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CoolingSeverity Low: usually safe to drive

P0125Insufficient Coolant Temperature for Closed Loop Fuel Control

What it means

After starting, the engine took too long to reach the temperature at which the ECU starts using the oxygen sensor to control the mixture.

Symptoms

  • Engine slow to warm up
  • Weak cabin heat
  • Higher fuel consumption

Common causes

  • Thermostat stuck open
  • Coolant temperature sensor reading low
  • Low coolant level

What to check first

  1. Graph coolant temperature from cold on a steady drive
  2. Feel or IR-check the top radiator hose: it should stay cool until the thermostat opens
  3. Check the coolant level
Can I drive with P0125? Usually yes. P0125 rarely affects how the car drives, but it keeps the check engine light on and can fail an emissions test.

Generic OBD-II meaning. Manufacturer-specific meanings and checks can differ; always check the service information for the car.

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P0125: questions and answers

What does P0125 mean?

P0125: Insufficient Coolant Temperature for Closed Loop Fuel Control. After starting, the engine took too long to reach the temperature at which the ECU starts using the oxygen sensor to control the mixture.

What are the symptoms of P0125?

Engine slow to warm up. Weak cabin heat. Higher fuel consumption.

What causes P0125?

Thermostat stuck open. Coolant temperature sensor reading low. Low coolant level.

How do you diagnose P0125?

1. Graph coolant temperature from cold on a steady drive 2. Feel or IR-check the top radiator hose: it should stay cool until the thermostat opens 3. Check the coolant level

Can I drive with P0125?

Usually yes. P0125 rarely affects how the car drives, but it keeps the check engine light on and can fail an emissions test.