What does the engine coolant temperature sensor do?

The engine coolant temperature sensor (ECTS) is a device used to measure the temperature of the engine coolant. This information is used by the engine control unit (ECU) to adjust the fuel mixture and ignition timing to ensure optimal engine performance and efficiency. The ECTS is typically located in the cylinder head or thermostat housing and is made up of a thermistor, which is a type of resistor whose resistance changes with temperature. As the temperature of the coolant increases, the resistance of the thermistor decreases, allowing more current to flow through it. This change in resistance is detected by the ECU, which uses it to calculate the coolant temperature.

The ECTS plays a crucial role in maintaining proper engine operation by providing accurate temperature readings to the ECU. Based on this information, the ECU can make necessary adjustments to fuel injection and ignition timing. For example, when the engine is cold, the ECU enriches the fuel mixture and advances the ignition timing to aid in starting and smooth running. As the engine warms up, the ECU adjusts the fuel mixture and ignition timing accordingly to achieve optimal combustion and efficiency.

A faulty ECTS can cause various issues with engine performance and fuel economy. Common symptoms of a faulty ECTS include:

- Engine overheating

- Poor fuel economy

- Engine stalling or rough idling

- Check engine light illumination

If you experience any of these symptoms, it is recommended to have your vehicle checked by a qualified mechanic to diagnose and replace a faulty ECTS if necessary.