Introduction of The Engine Coolant Temperature Sensor

What is the engine coolant temperature sensor?

The engine coolant temperature sensor (ECTS), also known as the coolant temperature sensor (CTS) or the ECT sensor, measures the temperature of the coolant/antifreeze mixture in the cooling system, indicating how much heat the engine is dissipating. The sensor works with the vehicle's electronic control unit (ECU) to continuously monitor the coolant temperature to ensure the engine is running at optimum temperature so that the fuel quantity and ignition point can be adapted accordingly. The ECT sensor is a high authority sensor when the engine is cold because the ignition timing is tailored to the engine coolant temperature. It also provides inputs for idle air control (IAC) position, oxygen sensor closed loop status, tank purge on/off time and idle speed.

Where is the engine coolant temperature sensor located?

The ECT sensor is usually located near the engine thermostat in the cylinder head or inside the thermostat housing. Many vehicles also have a second ECT sensor installed in a different part of the engine or radiator. You can locate the ECT sensor by consulting your repair manual or repair database.

How does the engine coolant temperature sensor work?

The ECT sensor is made of semiconductor materials that decrease in resistance as the temperature of the sensor increases. To get an accurate reading of the current engine temperature, the ECU sends a regulated voltage to the CTS. The resistance of the sensor changes with temperature, which is how the ECU monitors temperature changes. The ECU uses this reading to calculate coolant temperature and adjusts fuel injection, fuel mixing and ignition timing accordingly, and controls when the electric cooling fan is turned on and off.

Working principle of the engine coolant temperature sensor

Although there are many different types ECT sensor, such as, ECT sensor 4954905 for Cummins Engine Dodge Ram 2500, ECT sensor 500382599 for Case f3hfe613c, their working principle is roughly the same. The fuel management system uses the ECT sensor to detect the engine's operating temperature. Based on the sensor information, the control unit adjusts the injection time and firing angle according to the operating conditions. The sensor is a temperature sensor with a negative temperature coefficient. This means that the internal resistance decreases with increasing temperature.

The resistance of the temperature sensor changes as the temperature of the coolant changes. As the temperature increases, the resistance decreases, which reduces the voltage across the sensor. The control unit evaluates these voltage values because they are directly related to the coolant temperature (low temperatures lead to high voltage values on the sensor, high temperatures lead to low voltage values).

Types of the engine coolant temperature sensor

1. The temperature coefficient is negative. These are the most commonly used sensors in vehicle Their resistance decreases with increasing temperature.

2. The temperature coefficient is positive. Used in some older systems, where voltage and resistance increase with temperature.