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Everything you need to know about Coolant Temperature Sensors

06 Apr 2018

Category: Articles, Industry News

Have you ever wondered how the vehicle’s engine cooling system works, and whether an engine is working at the right temperature? Every vehicle engine needs coolant/antifreeze to run correctly and a coolant temperature sensor is critical to enable the monitoring of your engines temperature.

What is a coolant temperature sensor?

The engine coolant temperature sensor is a device which is used to measure the temperature of the coolant mix within the engine’s cooling system. The sensor works alongside the ECU (engine control unit) in a vehicle to continually monitor the temperature of the coolant, ensuring that the engine is running at the optimum settings.

The ECU then reads this temperature and calculates the coolant temperature, adjusting the fuel mix, ignition timing and fuel injection point accordingly. This information is also used to send a reading of the engine’s temperature to a gauge on a vehicle’s dashboard.

How can you spot a faulty coolant temperature sensor?

  • If the vehicle has become difficult to start when it is hot or cold.
  • If the fuel economy vehicle has become poor.
  • The engine may be misfiring or cutting out.
  • If black smoke has started to appear from the exhaust pipe.
  • If you have had an irregular reading on the engine temperature gauge on the vehicles dashboard.

Testing Procedure

To test the coolant temperature sensor, ensure the ignition is turned off, and then disconnect the sensor from its electrical connectors.

  1. If the switch is located high in the cooling system check the coolant levels. If the level is low then you will not be able to read the temperature of the coolant.
  2. Check wires/connectors for corrosion and damage and ensure that a good connection is achieved between the sensor and the ECU.
  3. Check the resistance of the part by connecting a multimeter to the sensor terminals. Compare the reading with the manufacturer’s specification, taking account of the temperature of the switch at the time. Also bear in mind that the resistance of some sensors will increase with temperature, and others will decrease.

Common Fault Codes

  • P0116 Engine Coolant Temperature Circuit Range/Performance Problem
  • P0117 Engine Coolant Temperature Circuit Low Input
  • P0118 Engine Coolant Temperature Circuit High Input
  • P0119 Engine Coolant Temperature Circuit Intermittent

Top Highlights

Cambiare Part Number Description Top App
VE375145 Coolant Temperature Sensor Toyota Yaris Toyota Yaris – 1.0 – 03-05
VE375144 Coolant Temperature Sensor Nissan Micra Nissan Micra – 1.2 – 03-10
VE375164 Coolant Temperature Sensor Renault Clio Renault Clio – 1.2 – 05-14


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