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P0126 Powertrain

Insufficient Coolant Temperature for Stable Operation

Coolant temperature stays below the value expected for stable engine operation. Almost always points to a thermostat stuck open or a sensor reading lower than the actual engine temperature.

Affected components

  • Thermostat
  • Coolant temperature sensor

Common causes

  • High likelihood: Thermostat stuck open

Diagnostic notes

  • The malfunction indicator lamp may illuminate
  • This code can affect emissions
  • A drive cycle may be required after repair

Related codes

Sources

Diagnostic information is provided for reference only. Confirm the code with a compatible scan tool and follow the vehicle manufacturer's service procedures before replacing components.

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