When the water temperature sensor fails, the temperature signal displayed when the cold car is started is still the temperature signal when the car is warm. The ECU cannot provide a signal that provides an excessively rich mixture. Therefore, it is not easy to start the engine cold car. In this case, check whether the water temperature sensor plug is in normal contact or replace the water temperature sensor.
For example: reading the data of the car's static engine (referred to when it is cold), it is found that the coolant temperature output by the engine ECU is 105 ° C, and the actual temperature of the engine at this time (set in winter) is only 1 ° C. Obviously, the water temperature signal received by the engine ECU is wrong, indicating that there is a problem with the water temperature sensor.
It should be noted that the sensor is an electronic original device on the automobile circuit. If this device is broken, there is little room for repair, only the replacement. If you want to test it, the simple method is to put the water temperature sensor into the heating cup (be careful not to submerge the plug part), and use the “resistance range” of the multimeter to measure. When the temperature rises, the resistance should be small. If there is no change, then this thing is broken.
If this part is tested with a diagnostic tool, it needs to be tested during a cold car.
The function of the water temperature sensor is to convert the temperature of the cooling water into an electrical signal. After the input to the ECU: 1. Correct the fuel injection amount; increase the fuel injection amount when the temperature is low. 2. Correct the ignition advance angle; increase the ignition advance angle at low temperatures, and postpone it to prevent detonation at high temperatures. 3. Affects the idling control valve; at low temperature, the ECU controls the idling control valve to act according to the water temperature sensing signal to increase the speed.