Functions and Classification of Automotive Temperature Sensors

Temperature sensors are widely used in automobiles, such as coolant temperature sensors (capteurs de température de l'eau), intake temperature sensors, transmission oil temperature sensors, etc.. The main function of these sensors is to monitor the temperature of different parts and feed back the data to the ECU to adjust the operating parameters of the engine and vehicle systems.

The next thing to consider is the type and working principle of the sensor. Commonly used ones are negative temperature coefficient thermistors (CTN), thermocouples, platinum resistance detectors (RDT), etc.. Parmi eux, NTC is the most widely used. Par exemple, the water temperature sensor uses the characteristic that the resistance of NTC decreases with increasing temperature. Silicon-based sensors such as KTY84 are used in higher precision occasions, such as oil temperature detection. The measurement range and accuracy of different sensors have their own characteristics. Par exemple, thermocouples are suitable for high temperature environments, but the accuracy is low; platinum resistance detectors have high accuracy but high cost.

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Hyundai ELANTRA water temperature sensor temperature sensor plug 3922003HA0 39220-03HA0

68217702AC is suitable for engine coolant temperature sensor

The installation location is also critical. Par exemple, the water temperature sensor is usually near the water jacket of the engine block or cylinder head, while the intake temperature sensor is in the intake pipe or air flow meter. The location of the external temperature sensor varies, some are in the front bumper, some are near the water tank, and the difference between different models is large. The choice of these locations directly affects the accuracy of the measurement and the durability of the sensor.

In terms of function, the temperature sensor has a great impact on vehicle performance. Abnormal water temperature sensors can cause problems such as difficult cold starts, unstable idle speed, and increased fuel consumption. Failure of the intake temperature sensor may cause an imbalance in the mixture ratio and affect power output. These failure cases illustrate the importance of sensors, especially the impact of data inaccuracy on ECU decision-making.

The fault handling section needs to summarize common problems and solutions. Par exemple, signal drift, line aging, physical damage, etc.. During diagnosis, the actual temperature can be compared by measuring resistance, voltage or data flow. Here we should emphasize the importance of regular maintenance and correct installation to avoid major failures caused by minor problems.

Enfin, the development of new technologies is also improving the performance of sensors. Par exemple, Continental’s eRTS sensor can directly measure the temperature of the motor rotor with an accuracy of ±3°C, reducing the use of rare earth materials. This innovation demonstrates the progress of temperature sensors in the field of electric vehicles.

Air charge temperature sensor for 13 -20 Volkswagen GTI Jetta GLI 06K907386D

Ambient temperature sensor for Chevrolet 10248414 SU1340

Temperature sensor for Buick Chevrolet 13276269

🔧 ‌I. Core types and technical principles‌
‌Coolant temperature sensor‌
‌Location‌: Engine cylinder block/cylinder head water jacket (mainstream position for 65% of models), near the thermostat or coolant shunt pipe.
‌Principle‌: Using negative temperature coefficient thermistor (CTN), the resistance drops to 0.3kΩ at 80℃ (2.5kΩ at 20℃).
‌Function‌: Correct low temperature injection amount (+30% cold start compensation), adjust ignition advance angle (-20℃ advance 8–12°), control idle speed (low temperature rises to 1200–1500rpm).

‌Intake air temperature sensor‌
‌Location‌: Intake pipe or inside air flow meter 5.
‌Impact‌: Abnormal signal leads to mixture imbalance, causing cold start difficulty or weak acceleration.

‌Transmission oil temperature sensor‌
‌Location‌: Inside the oil pan of the automatic transmission valve plate 5.
‌Function‌: Provide temperature basis for shift logic, oil pressure control and locking clutch.

‌Exterior/interior temperature sensor‌
‌Exterior‌: Behind the front bumper or the front wall of the cab, controlling the temperature zone of the automatic air conditioner.
‌Interior‌: The ventilation duct under the instrument panel monitors the ambient temperature of the cabin.

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Suitable for Audi, Volkswagen, Skoda water temperature sensor plug 038906081B 1830376

8Z0820535A 5QD820535 Applicable to Audi Volkswagen Air Conditioning Intake Temperature Sensor

⚙️ ‌II. Technological evolution and innovation‌

Breakthrough in precision measurement‌: The new eRTS sensor directly measures the motor rotor temperature through piezoelectric ultrasonic technology, with an accuracy increased from ±15℃ to ±3℃, reducing dependence on rare earth materials.
‌Material upgrade‌: The silicon-based KTY84 sensor can work at -40℃~300℃, and its linear resistance-temperature characteristics are suitable for high-temperature scenarios such as diesel injection systems.

⚠️ ‌III. Typical faults and diagnosis‌

Iv. Differences in installation position and impacts‌
‌Same function, different position‌: The external temperature sensor is located in the drain groove or front bumper of the Sagitar model, while some models are integrated under the rearview mirror.
‌Accuracy correlation‌: When the coolant sensor is in direct contact with the liquid, the error is ≤±15℃, and the indirect calculation (such as the motor stator inferring the rotor) has an error of up to 15℃.

💎 Summary
The temperature sensor is like the “nerve endings” of the car, and its accuracy directly affects the power output efficiency and energy consumption. Avec le développement de véhicules électriques, high-precision direct measurement technology (such as eRTS) is gradually replacing the indirect inference mode, promoting the refined revolution of the thermal management system. Regular detection of resistance characteristics and signal stability is the key to preventing systemic failures.