• The fault code P0126 indicates that the engine coolant temperature is below the thermostat regulating temperature. This may cause the engine to run poorly or not at all.

Possible Symptoms:

  • Illuminated check engine light

  • Poor engine performance

  • Decreased fuel efficiency

  • Overheating engine

Possible Causes:

  • Faulty thermostat

  • Low coolant level

  • Malfunctioning engine coolant temperature sensor

  • Faulty engine control module (ECM)

Related Parts:

  • Engine Coolant Temperature Sensor: The coolant temperature sensor measures the temperature of the engine coolant. Problems lead to engine overheating

Possible Solutions:

  • Replace the faulty thermostat

  • Check and refill the coolant level

  • Replace the malfunctioning engine coolant temperature sensor

  • Replace the engine control module (ECM) if necessary