What Causes the BMW 3 Series External Temperature to Occasionally Display Abnormally?

[StAnastasia]

For the BMW 3 Series, if the external temperature display is abnormal, it is necessary to check the wiring of the external temperature sensor. The external temperature sensor is located under the left front bumper. Try unplugging and reconnecting it to see if the issue resolves. If the wiring is fine, the temperature sensor might be faulty. In most vehicles, when an external temperature sensor fails, the temperature displayed on the dashboard will be abnormal. This can lead to a distorted air-fuel ratio in the engine and may cause the air conditioning system to malfunction or stop working altogether. Additional Information: 1. External Temperature Sensor: The car's external temperature sensor detects the ambient temperature and transmits it to the engine's ECU, converting it into an electrical signal. This determines the optimal temperature for the automatic air conditioning system without manual intervention, ensuring the most comfortable temperature. 2. Working Principle of the External Temperature Sensor: The external temperature sensor, also known as the ambient temperature sensor, is typically installed near the front bumper or grille. Its sensing element uses a negative temperature coefficient thermistor. The detection method for the external temperature sensor is similar to that of the coolant temperature sensor. You can measure its resistance with a multimeter in resistance mode. The normal resistance at room temperature should be between 1.6 to 1.8KΩ, with higher resistance at lower temperatures. If the resistance exceeds the specified value, it indicates an open circuit in the sensor wiring or poor contact in the connector, which can affect the normal operation of the vehicle's air conditioning system. Further inspection or replacement may be necessary.