The function of the first type of water temperature sensor is relatively simple, which is to drive the change of the water temperature gauge by changing the resistance of the sensor through its internal resistance value, indirectly telling people the working temperature of the engine. The second type, the water temperature sensor, has no structural changes, but its function is to provide an analog signal of temperature changes to the engine control unit. Its power supply voltage is provided by the control unit with a 5V power supply, and the signal returned to the control unit is a linear variation signal of 1.3V-3.8V. The main function is to inform the engine control unit of the temperature. On the other hand, its signal is crucial for the control unit. The main reason is that the engine has different working methods at different operating temperatures. For example, when the engine is below 86 degrees Celsius, it is necessary to spray 10% more fuel than normal temperature in order to quickly heat up the engine and reduce low-temperature wear. After the temperature rises to above 86 degrees, the engine needs to spray less oil, so the temperature regeneration should be slower. So its role is very important. If he has a problem and provides an incorrect signal to the engine control unit, such as providing a low engine temperature signal when the car is hot, does your car need to spray more oil, so it looks a bit wasteful.

But these two types of water temperature sensors operate under different voltage conditions. The sensor used for the water supply temperature gauge is 12V, while the sensor used for the engine control unit is 5V, so they cannot be interchanged. Moreover, their plug shapes themselves are different.
The difference between them is simple: the former has only one wire inside the plug, while the latter has two wires inside the plug used by the engine control unit. Don't make any mistakes, everyone.